Protocol Independent Multicast for IPv6 (IPv6 PIM) provides IPv6 multicast forwarding by leveraging IPv6 unicast static routes or IPv6 unicast routing tables generated by any IPv6 unicast routing protocol, such as RIPng, OSPFv3, IS-ISv6, or BGP4+. IPv6 PIM uses an IPv6 unicast routing table to perform reverse path forwarding (RPF) check to implement IPv6 multicast forwarding. Independent of the IPv6 unicast routing protocols running on the device, IPv6 multicast routing can be implemented as long as the corresponding IPv6 multicast routing entries are created through IPv6 unicast routes. IPv6 PIM uses the reverse path forwarding (RPF) mechanism to implement IPv6 multicast forwarding. When an IPv6 multicast packet arrives on an interface of the device, it is subject to an RPF check. If the RPF check succeeds, the device creates the corresponding routing entry and forwards the packet. If the RPF check fails, the device discards the packet. For more information about RPF, see the chapter “Configuring IPv6 multicast routing and forwarding.”

Based on the implementation mechanism, IPv6 PIM supports the following types:

· Protocol Independent Multicast–Dense Mode for IPv6 (IPv6 PIM-DM)

· Protocol Independent Multicast–Sparse Mode for IPv6 (IPv6 PIM-SM)

· Bidirectional Protocol Independent Multicast for IPv6 (IPv6 BIDIR-PIM)

· Protocol Independent Multicast Source-Specific Multicast for IPv6 (IPv6 PIM-SSM)

NOTE:

To facilitate description, a network comprising IPv6 PIM–supporting routers is referred to as an “IPv6 PIM domain” in this document.

IPv6 PIM-DM overview

IPv6 PIM-DM is a type of dense mode IPv6 multicast protocol. It uses the “push mode” for IPv6 multicast forwarding, and is suitable for small-sized networks with densely distributed IPv6 multicast members.

The basic implementation of IPv6 PIM-DM is as follows:

· IPv6 PIM-DM assumes that at least one IPv6 multicast group member exists on each subnet of a network, and therefore IPv6 multicast data is flooded to all nodes on the network. Then, branches without IPv6 multicast forwarding are pruned from the forwarding tree, leaving only those branches that contain receivers. This “flood and prune” process takes place periodically, that is, pruned branches resume IPv6 multicast forwarding when the pruned state times out and then data is re-flooded down these branches, and then are pruned again.

· When a new receiver on a previously pruned branch joins an IPv6 multicast group, to reduce the join latency, IPv6 PIM-DM uses the graft mechanism to resume IPv6 multicast data forwarding to that branch.

Generally speaking, the IPv6 multicast forwarding path is a source tree, namely a forwarding tree with the IPv6 multicast source as its “root” and IPv6 multicast group members as its “leaves”. Because the source tree is the shortest path from the IPv6 multicast source to the receivers, it is also called shortest path tree (SPT).

The working mechanism of IPv6 PIM-DM is summarized as follows:

· Neighbor discovery

· SPT establishment

· Graft

· Assert

Neighbor discovery

In an IPv6 PIM domain, a PIM router discovers IPv6 PIM neighbors, maintains IPv6 PIM neighboring relationships with other routers, and builds and maintains SPTs by periodically multicasting IPv6 PIM hello messages (hereinafter referred to as “hello messages”) to all other IPv6 PIM routers on the local subnet.

NOTE:

Every interface with IPv6 PIM enabled on a router sends hello messages periodically, and thus learns the IPv6 PIM neighboring information pertinent to the interface.

SPT establishment

The process of constructing an SPT is the “flood and prune” process.

1. In an IPv6 PIM-DM domain, an IPv6 multicast source first floods IPv6 multicast packets when it sends IPv6 multicast data to an IPv6 multicast group G: The packet is subject to an RPF check. If the packet passes the RPF check, the router creates an (S, G) entry and forwards the packet to all downstream nodes in the network. In the flooding process, an (S, G) entry is created on all the routers in the IPv6 PIM-DM domain.

2. Then, nodes without downstream receivers are pruned: A router having no down stream receivers sends a prune message to the upstream node to notify the upstream node to delete the corresponding interface from the outgoing interface list in the (S, G) entry and stop forwarding subsequent packets addressed to that IPv6 multicast group down to this node.

NOTE:

· An (S, G) entry contains the multicast source address S, IPv6 multicast group address G, outgoing interface list, and incoming interface.

· For a given IPv6 multicast stream, the interface that receives the IPv6 multicast stream is referred to as “upstream”, and the interfaces that forward the IPv6 multicast stream are referred to as “downstream”.

A prune process is first initiated by a leaf router. As shown in Figure 1, a router without any receiver attached to it (the router connected with Host A, for example) sends a prune message, and this prune process goes on until only necessary branches are left in the IPv6 PIM-DM domain. These branches constitute the SPT.

Figure 1 SPT establishment in an IPv6 PIM-DM domain

The “flood and prune” process takes place periodically. A pruned state timeout mechanism is provided. A pruned branch restarts multicast forwarding when the pruned state times out and then is pruned again when it no longer has any multicast receiver.

NOTE:

Pruning has a similar implementation in IPv6 PIM-SM.

Graft

When a host attached to a pruned node joins an IPv6 multicast group, to reduce the join latency, IPv6 PIM-DM uses the graft mechanism to resume IPv6 multicast data forwarding to that branch. The process is as follows:

1. The node that needs to receive IPv6 multicast data sends a graft message hop by hop toward its upstream node, as a request to join the SPT again.

2. Upon receiving this graft message, the upstream node puts the interface on which the graft was received into the forwarding state and responds with a graft-ack message to the graft sender.

3. If the node that sent a graft message does not receive a graft-ack message from its upstream node, it keeps sending graft messages at a configurable interval until it receives an acknowledgment from its upstream node.

Assert

If multiple multicast routers exist on a multi-access subnet, duplicate IPv6 multicast packets may flow to the same subnet. To shut off duplicate flows, the assert mechanism is used for election of a single IPv6 multicast forwarder on a multi-access network.

Figure 2 Assert mechanism

As shown in Figure 2, after Router A and Router B receive an (S, G) IPv6 multicast packet from the upstream node, they both forward the packet to the local subnet. As a result, the downstream node Router C receives two identical multicast packets, and both Router A and Router B, on their own local interface, receive a duplicate IPv6 multicast packet forwarded by the other. Upon detecting this condition, both routers send an assert message to all IPv6 PIM routers on the local subnet through the interface on which the packet was received. The assert message contains the following information: the multicast source address (S), the multicast group address (G), and the preference and metric of the IPv6 unicast route/IPv6 MBGP route/IPv6 multicast static route to the source. By comparing these parameters, either Router A or Router B becomes the unique forwarder of the subsequent (S, G) IPv6 multicast packets on the multi-access subnet. The comparison process is as follows:

1. The router with a higher route preference to the source wins.

2. If both routers have the same route preference to the source, the router with a smaller metric to the source wins.

3. If there is a tie in the route metric to the source, the router with a higher link-local address of the local interface wins.

IPv6 PIM-SM overview

IPv6 PIM-DM uses the “flood and prune” principle to build SPTs for IPv6 multicast data distribution. Although an SPT has the shortest path, it is built with a low efficiency. Therefore the PIM-DM mode is not suitable for large-and medium-sized networks.

IPv6 PIM-SM is a type of sparse mode IPv6 multicast protocol. It uses the “pull mode” for IPv6 multicast forwarding, and is suitable for large- and medium-sized networks with sparsely and widely distributed IPv6 multicast group members.

The basic implementation of IPv6 PIM-SM is as follows:

· IPv6 PIM-SM assumes that no hosts need to receive IPv6 multicast data. In the IPv6 PIM-SM mode, routers must specifically request a particular IPv6 multicast stream before the data is forwarded to them. The core task for IPv6 PIM-SM to implement IPv6 multicast forwarding is to build and maintain rendezvous point trees (RPTs). An RPT is rooted at a router in the IPv6 PIM domain as the common node, or rendezvous point (RP), through which the IPv6 multicast data travels along the RPT and reaches the receivers.

· When a receiver is interested in the IPv6 multicast data addressed to a specific IPv6 multicast group, the router connected to this receiver sends a join message to the RP corresponding to that IPv6 multicast group. The path along which the message goes hop by hop to the RP forms a branch of the RPT.

· When a multicast source sends an IPv6 multicast packet to an IPv6 multicast group, the source-side designated router (DR) first registers the multicast source with the RP by sending a register message to the RP by unicast. The arrival of this message at the RP triggers the establishment of an SPT. Then, the multicast source sends subsequent IPv6 multicast packets along the SPT to the RP. Upon reaching the RP, the IPv6 multicast packet is duplicated and delivered to the receivers along the RPT.

NOTE:

IPv6 multicast traffic is duplicated only where the distribution tree branches, and this process automatically repeats until the IPv6 multicast traffic reaches the receivers.

The working mechanism of IPv6 PIM-SM is summarized as follows:

· Neighbor discovery

· DR election

· RP discovery

· Embedded RP

· RPT establishment

· IPv6 Multicast source registration

· SPT switchover

· Assert

Neighbor discovery

IPv6 PIM-SM uses a similar neighbor discovery mechanism as IPv6 PIM-DM does. For more information, see “Neighbor discovery.”

DR election

IPv6 PIM-SM also uses hello messages to elect a designated router (DR) for a multi-access network (such as an Ethernet network). The elected DR will be the only multicast forwarder on this multi-access network.

In the case of a multi-access network, a DR must be elected, no matter this network connects to IPv6 multicast sources or to receivers. The DR at the receiver side sends join messages to the RP; the DR at the IPv6 multicast source side sends register messages to the RP.

NOTE:

· A DR is elected on a multi-access subnet by means of comparison of the priorities and IPv6 link-local addresses carried in hello messages.

· MLD must be enabled on a receiver-side device that acts as a DR before receivers attached to this device can join IPv6 multicast groups through this DR.

For more information about MLD, see the chapter “Configuring MLD.”

Figure 3 DR election

As shown in Figure 3, the DR election process is as follows:

1. Routers on the multi-access network send hello messages to one another. The hello messages contain the router priority for DR election. The router with the highest DR priority becomes the DR.

2. In the case of a tie in the router priority, or if any router in the network does not support carrying the DR-election priority in hello messages, The router with the highest IPv6 link-local address wins the DR election.

When the DR works abnormally, a timeout in receiving hello message triggers a new DR election process among the other routers.

RP discovery

The RP is the core of an IPv6 PIM-SM domain. For a small-sized, simple network, one RP is enough for forwarding IPv6 multicast information throughout the network, and the position of the RP can be statically specified on each router in the IPv6 PIM-SM domain. In most cases, however, an IPv6 PIM-SM network covers a wide area and a huge amount of IPv6 multicast traffic needs to be forwarded through the RP. To lessen the RP burden and optimize the topological structure of the RPT, multiple candidate-RPs (C-RPs) can be configured in an IPv6 PIM-SM domain, among which an RP is dynamically elected through the bootstrap mechanism. Each elected RP serves a different multicast group range. For this purpose, a bootstrap router (BSR) must be configured. The BSR serves as the administrative core of an IPv6 PIM-SM domain. An IPv6 PIM-SM domain can have only one BSR, but can have multiple candidate-BSRs (C-BSRs). Once the BSR fails, a new BSR is automatically elected from the C-BSRs through the bootstrap mechanism to avoid service interruption.

NOTE:

· An RP can serve multiple IPv6 multicast groups or all IPv6 multicast groups. Only one RP can serve a given IPv6 multicast group at a time.

· A device can serve as a C-RP and a C-BSR at the same time.

As shown in Figure 4, each C-RP periodically unicasts its advertisement messages (C-RP-Adv messages) to the BSR. A C-RP-Adv message contains the address and priority of the advertising C-RP and the IPv6 multicast group range it servers. The BSR collects these advertisement messages and chooses the appropriate C-RP information for each IPv6 multicast group to form an RP-set, which is a database of mappings between IPv6 multicast groups and RPs. The BSR then encapsulates the RP-set in the bootstrap messages it periodically originates and floods the bootstrap messages to the entire IPv6 PIM-SM domain.

Figure 4 BSR messages and C-RP advertisement messages

Based on the information in the RP-sets, all routers in the network can calculate the location of the corresponding RPs based on the following rules:

1. The C-RP with the highest priority wins.

2. If all the C-RPs have the same priority, their hash values are calculated through the hashing algorithm. The C-RP with the largest hash value wins.

3. If all the C-RPs have the same priority and hash value, the C-RP has the highest IP address wins.

The hashing algorithm used for RP calculation is: Value (G, M, C_i) = (1103515245 * ( (1103515245 * (G & M) + 12345) XOR C_i) + 12345) mod 2³¹. The table below gives the meanings of the values in this algorithm.

Table 1 Values in the hashing algorithm

Value	Description
Value	Hash value
G	The digest from the exclusive-or (XOR) operation between the 32-bit segments of the IPv6 multicast group address. For example, if the IPv6 multicast address is FF0E:C20:1A3:63::101, G = 0xFF0E0C20 XOR 0x01A30063 XOR 0x00000000 XOR 0x00000101
M	Hash mask length
C_i	The digest from the exclusive-or (XOR) operation between the 32-bit segments of the C-RP IPv6 address. For example, if the IPv6 address of the C-RP is 3FFE:B00:C18:1::10, C_i = 0x3FFE0B00 XOR 0x0C180001 XOR 0x00000000 XOR 0x00000010
&	Logical operator of “and”
XOR	Logical operator of “exclusive-or”
mod	Modulo operator, which gives the remainder of an integer division

Embedded RP

The embedded RP mechanism allows a router to resolve the RP address from an IPv6 multicast address so that the IPv6 multicast group is mapped to an RP, which can take the place of the statically configured RP or the RP dynamically calculated based on the BSR mechanism. The DR does not need to know the RP address beforehand. The specific process is as follows.

· At the receiver side:

a. A receiver host initiates an MLD report to announce its joining an IPv6 multicast group.

b. Upon receiving the MLD report, the receiver-side DR resolves the RP address embedded in the IPv6 multicast address, and sends a join message to the RP.

· At the IPv6 multicast source side:

a. The IPv6 multicast source sends IPv6 multicast traffic to the IPv6 multicast group.

b. The source-side DR resolves the RP address embedded in the IPv6 multicast address, and sends a register message to the RP.

RPT establishment

Figure 5 RPT establishment in an IPv6 PIM-SM domain

As shown in Figure 5, the process of building an RPT is as follows:

1. When a receiver joins an IPv6 multicast group G, it uses an MLD report message to inform the directly connected DR.

2. Upon getting the IPv6 multicast group G’s receiver information, the DR sends a join message, which is hop by hop forwarded to the RP corresponding to the multicast group.

3. The routers along the path from the DR to the RP form an RPT branch. Each router on this branch generates a (*, G) entry in its forwarding table. The * means any IPv6 multicast source. The RP is the root, while the DRs are the leaves, of the RPT.

The IPv6 multicast data addressed to the IPv6 multicast group G flows through the RP, reaches the corresponding DR along the established RPT, and finally is delivered to the receiver.

When a receiver is no longer interested in the IPv6 multicast data addressed to a multicast group G, the directly connected DR sends a prune message, which goes hop by hop along the RPT to the RP. Upon receiving the prune message, the upstream node deletes the interface connected with this downstream node from the outgoing interface list and checks whether it has receivers for that IPv6 multicast group. If not, the router continues to forward the prune message to its upstream router.

Multicast source registration

The purpose of IPv6 multicast source registration is to inform the RP about the existence of the IPv6 multicast source.

Figure 6 IPv6 multicast source registration

As shown in Figure 6, the IPv6 multicast source registers with the RP as follows:

1. When the IPv6 multicast source S sends the first IPv6 multicast packet to IPv6 multicast group G, the DR directly connected with the multicast source, upon receiving the multicast packet, encapsulates the packet in a register message, and sends the message to the corresponding RP by unicast.

2. When the RP receives the register message, it extracts the multicast packet from the register message and forwards the multicast IPv6 multicast packet down the RPT, and sends an (S, G) join message hop by hop toward the IPv6 multicast source. Thus, the routers along the path from the RP to the IPv6 multicast source form an SPT branch. Each router on this branch generates an (S, G) entry in its forwarding table. The DR at the IPv6 multicast source side is the root, while the RP is the leaf, of the SPT.

3. The subsequent IPv6 multicast data from the IPv6 multicast source travels along the established SPT to the RP, and then the RP forwards the data along the RPT to the receivers. When the IPv6 multicast traffic arrives at the RP along the SPT, the RP sends a register-stop message to the source-side DR by unicast to stop the source registration process.

NOTE:

The RP is configured to initiate an SPT switchover as described in this section. Otherwise, the DR at the IPv6 multicast source side keeps encapsulating multicast data in register messages and the registration process will not stop unless no outgoing interfaces exist in the (S, G) entry on the RP.

Switchover to SPT

NOTE:

A router is taken as an example in this section. As compared with the SPT switchover on a router, an SPT switchover process is implemented in a simpler way on a switch.

In an IPv6 PIM-SM domain, an IPv6 multicast group corresponds to one RP and one RPT. Before the SPT switchover takes place, the DR at the IPv6 multicast source side encapsulates all multicast data destined to the multicast group in register messages and sends these messages to the RP. Upon receiving these register messages, the RP abstracts the multicast data and sends the multicast data down the RPT to the DRs at the receiver side. The RP acts as a transfer station for all IPv6 multicast packets. The whole process involves three issues as follows:

· The DR at the source side and the RP need to implement complicated encapsulation and decapsulation of IPv6 multicast packets.

· IPv6 multicast packets are delivered along a path that is not necessarily the shortest one.

· When the IPv6 multicast traffic increases, a great burden is added to the RP, increasing the risk of failure.

To solve the issues, IPv6 PIM-SM allows an RP or the DR at the receiver side to initiate an SPT switchover process when the traffic rate exceeds the threshold:

1. The RP initiates an SPT switchover process

The RP can periodically check the passing-by IPv6 multicast packets. Once it finds that the traffic rate exceeds a configurable threshold, the RP sends an (S, G) join message hop by hop toward the IPv6 multicast source to establish an SPT between the DR at the source side and the RP. Subsequent IPv6 multicast data travels along the established SPT to the RP.

NOTE:

For more information about the SPT switchover initiated by the RP, see “Multicast source registration.”

2. The receiver-side DR initiates an SPT switchover process

Upon discovering that the traffic rate exceeds a configurable threshold, the receiver-side DR initiates an SPT switchover process, as follows:

¡ The receiver-side DR sends an (S, G) join message hop by hop toward the IPv6 multicast source. When the join message reaches the source-side DR, all the routers on the path have installed the (S, G) entry in their forwarding table, and thus an SPT branch is established.

¡ When the IPv6 multicast packets travel to the router where the RPT and the SPT deviate, the router drops the multicast packets received from the RPT and sends an RP-bit prune message hop by hop to the RP. Upon receiving this prune message, the RP sends a prune message toward the IPv6 multicast source (suppose only one receiver exists). Thus, SPT switchover is completed.

¡ Finally, IPv6 multicast data is directly sent from the source to the receivers along the SPT.

IPv6 PIM-SM builds SPTs through SPT switchover more economically than IPv6 PIM-DM does through the “flood and prune” mechanism.

Assert

IPv6 PIM-SM uses the similar assert mechanism as IPv6 PIM-DM does. For more information, see “Assert.”

IPv6 BIDIR-PIM overview

In some many-to-many applications, such as multi-side video conference, there may be multiple receivers interested in multiple IPv6 multicast sources simultaneously. With IPv6 PIM-DM or IPv6 PIM-SM, each router along the SPT must create an (S, G) entry for each IPv6 multicast source, consuming a lot of system resources. IPv6 BIDIR-PIM is introduced to address this problem. Derived from IPv6 PIM-SM, IPv6 BIDIR-PIM builds and maintains bidirectional RPTs, each of which is rooted at an RP and connects IPv6 multiple multicast sources with multiple receivers. Traffic from the IPv6 multicast sources is forwarded through the RP to the receivers along the bidirectional RPT. In this case, each router needs to maintain only a (*, G) multicast routing entry, saving system resources.

IPv6 BIDIR-PIM is suitable for networks with dense multicast sources and dense receivers.

The working mechanism of IPv6 BIDIR-PIM is summarized as follows:

· Neighbor discovery

· RP discovery

· DF election

· Bidirectional RPT building

Neighbor discovery

IPv6 BIDIR-PIM uses the same neighbor discovery mechanism as IPv6 PIM-SM does. For more information, see “Neighbor discovery.”

RP discovery

IPv6 BIDIR-PIM uses the same RP discovery mechanism as IPv6 PIM-SM does. For more information, see “RP discovery.”

In IPv6 PIM-SM, an RP must be specified with a real IPv6 address. In IPv6 BIDIR-PIM, however, an RP can be specified with a virtual IPv6 address, which is called the rendezvous point address (RPA). The link corresponding to the RPA’s subnet is called the rendezvous point link (RPL). All interfaces connected to the RPL can act as RPs, which back up one another.

NOTE:

In IPv6 BIDIR-PIM, an RPF interface is the interface pointing to an RP, and an RPF neighbor is the address of the next hop to the RP.

DF election

On a network segment with multiple multicast routers, the same multicast packets may be forwarded to the RP repeatedly. To address this issue, IPv6 BIDIR-PIM uses a DF election mechanism to elect a unique designated forwarder (DF) for each RP on every network segment within the IPv6 BIDIR-PIM domain, and allows only the DF to forward multicast data to the RP.

NOTE:

DF election is not necessary for an RPL.

Figure 7 DF election

As shown in Figure 7, without the DF election mechanism, both Router B and Router C can receive multicast packets from Route A, and they may both forward the packets to downstream routers on the local subnet. As a result, the RP (Router E) receives duplicate multicast packets. With the DF election mechanism, once receiving the RP information, Router B and Router C initiate a DF election process for the RP:

1. Router B and Router C multicast DF election messages to all PIM routers (224.0.0.13). The election messages carry the RP’s address, and the priority and metric of the unicast route, MBGP route, or multicast static route to the RP.

2. The router with a route of the highest priority becomes the DF.

3. In the case of a tie, the router with the route with the lowest metric wins the DF election.

4. In the case of a tie in the metric, the router with the highest link-local IPv6 address wins.

Bidirectional RPT building

A bidirectional RPT comprises two parts: receiver-side RPT and source-side RPT. The receiver-side RPT is rooted at the RP and takes the routers directly connected with the receivers as leaves. The source-side RPT is also rooted at the RP but takes the routers directly connected with the IPv6 multicast sources as leaves. The processes for building these two parts are different.

Figure 8 RPT building at the receiver side

As shown in Figure 8, the process for building a receiver-side RPT is similar to that for building an RPT in IPv6 PIM-SM:

1. When a receiver joins IPv6 multicast group G, it uses an MLD message to inform the directly connected router.

2. Upon getting the receiver information, the router sends a join message, which is forwarded hop by hop to the RP of the IPv6 multicast group.

3. The routers along the path from the receiver’s directly connected router to the RP form an RPT branch, and each router on this branch adds a (*, G) entry to its forwarding table. The * means any IPv6 multicast source.

When a receiver is no longer interested in the multicast data addressed to IPv6 multicast group G, the directly connected router sends a prune message, which goes hop by hop along the reverse direction of the RPT to the RP. Upon receiving the prune message, each upstream node deletes the interface connected with the downstream node from the outgoing interface list and checks whether it has receivers in that IPv6 multicast group. If not, the router continues to forward the prune message to its upstream router.

Figure 9 RPT building at the multicast source side

As shown in Figure 9, the process of building a source-side RPT is relatively simple:

1. When an IPv6 multicast source sends IPv6 multicast packets to IPv6 multicast group G, the DF in each network segment unconditionally forwards the packets to the RP.

2. The routers along the path from the source’s directly connected router to the RP form an RPT branch. Each router on this branch adds a (*, G) entry to its forwarding table. The * means any IPv6 multicast source.

After a bidirectional RPT is built, multicast traffic is forwarded along the source-side RPT and receiver-side RPT from IPv6 multicast sources to receivers.

NOTE:

If a receiver and an IPv6 multicast source are at the same side of the RP, the source-side RPT and the receiver-side RPT may meet at a node before reaching the RP. In this case, IPv6 multicast packets are directly forwarded by the node to the receiver, instead of by the RP.

IPv6 administrative scoping overview

Division of IPv6 PIM-SM domains

Typically, an IPv6 PIM-SM/IPv6 BIDIR-PIM domain contains only one BSR, which is responsible for advertising RP-set information within the entire IPv6 PIM-SM/IPv6 BIDIR-PIM domain. The information for all multicast groups is forwarded within the network scope administered by the BSR. We call this IPv6 non-scoped BSR mechanism.

To implement refined management, an IPv6 PIM-SM/IPv6 BIDIR-PIM domain can be divided into one IPv6 global scope zone and multiple IPv6 administratively scoped zones (IPv6 admin-scope zones). We call this IPv6 administrative scoping mechanism.

The IPv6 administrative scoping mechanism effectively releases stress on the management in a single-BSR domain and enables provision of zone-specific services using private group addresses.

IPv6 admin-scope zones correspond to IPv6 multicast groups with different scope values in their group addresses. The boundary of the IPv6 admin-scope zone is formed by zone border routers (ZBRs). Each IPv6 admin-scope zone maintains one BSR, which serves multicast groups within a specific scope. IPv6 multicast protocol packets, such as assert messages and bootstrap messages, for a specific group range cannot cross the IPv6 admin-scope zone boundary. IPv6 multicast group ranges served by different IPv6 admin-scope zones can overlap. An IPv6 multicast group is valid only within its local IPv6 admin-scope zone, functioning as a private group address.

The IPv6 global scope zone maintains a BSR, which serves the IPv6 multicast groups with the Scope field in their group addresses being 14.

Relationship between IPv6 admin-scope zones and the IPv6 global scope zone

The IPv6 global scope zone and each IPv6 admin-scope zone have their own C-RPs and BSRs. These devices are effective only in their respective IPv6 admin-scope zones. Namely, BSR election and RP election are implemented independently within each IPv6 admin-scope zone. Each IPv6 admin-scope zone has its own boundary. The multicast information cannot cross this border in either direction. A better understanding of the IPv6 global scope zone and IPv6 admin-scope zones should be based on two aspects: geographical space and group address range.

1. Geographical space

IPv6 admin-scope zones are logical zones specific to particular multicast groups. The multicast packets of these multicast groups are confined within the local IPv6 admin-scope zone and cannot cross the boundary of the zone.

Figure 10 Relationship between admin-scope zones and the global scope zone in geographic space

As shown in Figure 10, for multicast groups with the same Scope field in their group addresses, IPv6 admin-scope zones must be geographically separated from one another. Namely, a router must not serve different admin-scope zones. In other words, different admin-scope zones contain different routers, whereas the global scope zone covers all routers in the IPv6 PIM-SM/IPv6 BIDIR-PIM domain. Multicast packets that do not belong to any admin-scope zones can be transmitted in the entire IPv6 PIM-SM/IPv6 BIDIR-PIM domain.

2. In terms of multicast group address Scope field

As shown in Figure 11, the Scope field in each IPv6 multicast group address indicates the admin-scope zone the corresponding multicast group belongs to.

Figure 11 IPv6 multicast address format

The admin-scope zone range increases with the value of the Scope field. For example, value E indicates IPv6 global scope, which contains other admin-scope zones with the Scope field values smaller than E. Possible values of the Scope field are given in Table 2.

Table 2 Values of the Scope field

Value	Meaning	Remarks
0, F	Reserved	—
1	Interface-local scope	—
2	Link-local scope	—
3	Subnet-local scope	IPv6 admin-scope zone
4	Admin-local scope	IPv6 admin-scope zone
5	Site-local scope	IPv6 admin-scope zone
6, 7, 9 through D	Unassigned	IPv6 admin-scope zone
8	Organization-local scope	IPv6 admin-scope zone
E	Global scope	IPv6 global-scope zone

IPv6 PIM-SSM overview

The source-specific multicast (SSM) model and the any-source multicast (ASM) model are two opposite models. Presently, the ASM model includes the IPv6 PIM-DM and IPv6 PIM-SM modes. The SSM model can be implemented by leveraging part of the IPv6 PIM-SM technique, and it is also called IPv6 PIM-SSM.

In actual application, MLDv2 and part of IPv6 PIM-SM technique is adopted to implement the SSM model. In the SSM model, receivers know exactly where an IPv6 multicast source is located by means of advertisements, consultancy, and so on. Therefore, no RP is needed, no RPT is required, and is no source registration process is needed for the purpose of discovering IPv6 multicast sources in other IPv6 PIM domains.

The working mechanism of the IPv6 PIM-SSM is summarized as follows:

· Neighbor discovery

· DR election

· SPT building

Neighbor discovery

IPv6 PIM-SSM uses the same neighbor discovery mechanism as in IPv6 PIM-SM. For more information, see “Neighbor discovery.”

DR election

IPv6 PIM-SSM uses the same DR election mechanism as in IPv6 PIM-SM. For more information, see “DR election.”

SPT building

Whether to build an RPT for IPv6 PIM-SM or an SPT for IPv6 PIM-SSM depends on whether the IPv6 multicast group the receiver is to join falls in the IPv6 SSM group range (the IPv6 SSM group range reserved by IANA is FF3x::/32, where x represents any legal address scope).

Figure 12 Building an SPT in IPv6 PIM-SSM

As shown in Figure 12, Hosts B and C are IPv6 multicast information receivers. They send an MLDv2 report message to the respective DRs to announce that they are interested in the information of the specific IPv6 multicast source S and that sent to the IPv6 multicast group G.

The DR that has received the report first checks whether the IPv6 group address in this message falls in the IPv6 SSM group range:

· If so, the IPv6 PIM-SSM model is built: the DR sends a channel subscription message hop by hop toward the IPv6 multicast source S. An (S, G) entry is created on all routers on the path from the DR to the source. Thus, an SPT is built in the network, with the source S as its root and receivers as its leaves. This SPT is the transmission channel in IPv6 PIM-SSM.

· If not, the IPv6 PIM-SM process is followed: the receiver-side DR sends a (*, G) join message to the RP, and the source-side DR registers the IPv6 multicast source.

NOTE:

In IPv6 PIM-SSM, the “channel” concept is used to refer to an IPv6 multicast group, and the “channel subscription” concept is used to refer to a join message.

Relationships among IPv6 PIM protocols

In an IPv6 PIM network, IPv6 PIM-DM cannot work with IPv6 PIM-SM, IPv6 BIDIR-PIM, or IPv6 PIM-SSM. However, IPv6 PIM-SM, IPv6 BIDIR-PIM, and IPv6 PIM-SSM can work together. When they work together, which one is chosen for a receiver trying to join a group depends, as shown in Figure 13.

Figure 13 Relationships among IPv6 PIM protocols

NOTE:

For more information about MLD SSM mapping, see the chapter “Configuring MLD.”

Protocols and standards

IPv6 PIM-related specifications are as follows:

· RFC 4601: Protocol Independent Multicast-Sparse Mode(PIM-SM):Protocol Specification (Revised)

· RFC 3973: Protocol Independent Multicast-Dense Mode(PIM-DM):Protocol Specification (Revised)

· RFC 3956: Embedding the Rendezvous Point (RP) Address in an IPv6 Multicast Address

· RFC 4607: Source-Specific Multicast for IP

· RFC 5015: Bidirectional Protocol Independent Multicast (BIDIR-PIM)

· RFC 5059: Bootstrap Router (BSR) Mechanism for Protocol Independent Multicast (PIM)

· Draft-ietf-ssm-overview-05: An Overview of Source-Specific Multicast (SSM)

Configuring IPv6 PIM-DM

IPv6 PIM-DM configuration task list

Complete these tasks to configure IPv6 PIM-DM:

Task	Remarks
Enabling IPv6 PIM-DM	Required
Enabling state-refresh capability	Optional
Configuring state refresh parameters	Optional
Configuring IPv6 PIM-DM graft retry period	Optional
Configuring IPv6 PIM common features	Optional

Configuration prerequisites

Before configuring IPv6 PIM-DM, complete the following task:

· Enable IPv6 forwarding and configure any IPv6 unicast routing protocol so that all devices in the domain are interoperable at the network layer.

· Determine the interval between state refresh messages.

· Determine the minimum time to wait before receiving a new refresh message.

· Determine the hop limit value of state-refresh messages.

· Determine the graft retry period.

Enabling IPv6 PIM-DM

With IPv6 PIM-DM enabled, a router sends hello messages periodically to discover IPv6 PIM neighbors and processes messages from the IPv6 PIM neighbors. When deploying an IPv6 PIM-DM domain, you are recommended to enable IPv6 PIM-DM on all non-border interfaces of routers.

To enable IPv6 PIM-DM:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enable IPv6 multicast routing.	multicast ipv6 routing-enable	Disable by default
3. Enter interface view.	interface interface-type interface-number	N/A
4. Enable IPv6 PIM-DM.	pim ipv6 dm	Disabled by default

CAUTION:

· All the interfaces of the same device must work in the same IPv6 PIM mode.

· MLD snooping is not allowed in a VLAN after IPv6 PIM-DM is enabled on the virtual interface of the VLAN, and vice versa.

· IPv6 PIM-DM cannot be used for IPv6 multicast groups in the IPv6 SSM group range.

NOTE:

For more information about the multicast ipv6 routing-enable command, see IP Multicast Command Reference.

Enabling state-refresh capability

Pruned interfaces resume multicast forwarding when the pruned state times out. To prevent this, the router directly connected with the IPv6 multicast source periodically sends an (S, G) state-refresh message, which is forwarded hop by hop along the initial flooding path of the IPv6 PIM-DM domain, to refresh the prune timer state of all the routers on the path. A multi-access subnet can have the state-refresh capability only if the state-refresh capability is enabled on all IPv6 PIM routers on the subnet.

To enable the state-refresh capability:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter interface view.	interface interface-type interface-number	N/A
3. Enable the state-refresh capability.	pim ipv6 state-refresh-capable	Optional Enabled by default

Configuring state refresh parameters

The router directly connected with the multicast source periodically sends state-refresh messages. You can configure the interval for sending such messages.

A router may receive multiple state-refresh messages within a short time, of which some may be duplicated messages. To keep a router from receiving such duplicated messages, you can configure the time the router must wait before receiving the next state-refresh message. If a new state-refresh message is received within the waiting time, the router discards it. If this timer times out, the router accepts a new state-refresh message, refresh its own IPv6 PIM-DM state, and reset the waiting timer.

The hop limit value of a state-refresh message decrements by 1 whenever it passes a router before it is forwarded to the downstream node until the hop limit value comes down to 0. In a small network, a state-refresh message may cycle in the network. To effectively control the propagation scope of state-refresh messages, you need to configure an appropriate hop limit value based on the network size.

It is recommended to perform the following configurations on all routers in the IPv6 PIM domain.

To configure state-refresh parameters:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter IPv6 PIM view.	pim ipv6	N/A
3. Configure the interval between state-refresh messages.	state-refresh-interval interval	Optional 60 seconds by default
4. Configure the time to wait before receiving a new state-refresh message.	state-refresh-rate-limit interval	Optional 30 seconds by default
5. Configure the hop limit value of state-refresh messages.	state-refresh-hoplimit hoplimit-value	Optional 255 by default

Configuring IPv6 PIM-DM graft retry period

In IPv6 PIM-DM, graft is the only type of message that uses the acknowledgment mechanism. In an IPv6 PIM-DM domain, if a router does not receive a graft-ack message from the upstream router within the specified time after it sends a graft message, the router keeps sending new graft messages at a configurable interval, namely graft retry period, until it receives a graft-ack from the upstream router.

To configure IPv6 PIM-DM graft retry period:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter interface view.	interface interface-type interface-number	N/A
3. Configure graft retry period.	pim ipv6 timer graft-retry interval	Optional 3 seconds by default

NOTE:

For more information about the configuration of other timers in IPv6 PIM-DM, see “Configuring IPv6 PIM common timers.”

Configuring IPv6 PIM-SM

IPv6 PIM-SM configuration task list

Complete these tasks to configure IPv6 PIM-SM:

Task		Remarks
Enabling IPv6 PIM-SM		Required.
Configuring an RP	Configuring a static RP	Required. Use one of these approaches.
	Configuring a C-RP
	Enabling embedded RP
	Configuring C-RP timers globally	Optional.
Configuring a BSR	Configuring a C-BSR	Required.
	Configuring an IPv6 PIM domain border	Optional.
	Configuring C-BSR parameters globally	Optional.
	Configuring C-BSR timers	Optional.
	Disabling BSM semantic fragmentation	Optional.
Configuring IPv6 administrative scoping		Optional.
Configuring IPv6 multicast source registration		Optional.
Configuring SPT switchover		Optional.
Configuring IPv6 PIM common features		Optional.

Configuration prerequisites

Before configuring IPv6 PIM-SM, complete the following task:

· Enable IPv6 forwarding and configure any IPv6 unicast routing protocol so that all devices in the domain are interoperable at the network layer.

· Determine the The IP address of a static RP and the ACL that defines the range of IPv6 multicast groups to be served by the static RP.

· Determine the C-RP priority and the ACL that defines the range of IPv6 multicast groups to be served by each C-RP.

· Determine the legal C-RP address range and the ACL that defines the range of IPv6 multicast groups to be served.

· Determine the C-RP-Adv interval.

· Determine the C-RP timeout timer.

· Determine the C-BSR priority.

· Determine the hash mask length.

· Determine the IPv6 ACL that defines the legal BSR address range.

· Determine the BS period.

· Determine the BS timeout timer.

· Determine the IPv6 ACL for register message filtering.

· Determine the register suppression timer.

· Determine the register probe timer.

· Determine the IPv6 ACL rule and sequencing rule for SPT switchover.

Enabling IPv6 PIM-SM

With IPv6 PIM-SM enabled, a router sends hello messages periodically to discover IPv6 PIM neighbors and processes messages from the IPv6 PIM neighbors. When deploying an IPv6 PIM-SM domain, you are recommended to enable IPv6 PIM-SM on all non-border interfaces of the routers.

To enable IPv6 PIM-SM:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enable IPv6 multicast routing.	multicast ipv6 routing-enable	Disable by default
3. Enter interface view.	interface interface-type interface-number	N/A
4. Enable IPv6 PIM-SM.	pim ipv6 sm	Disabled by default

CAUTION:

· All the interfaces of the same device must work in the same IPv6 PIM mode.

· MLD snooping is not allowed in a VLAN after IPv6 PIM-SM is enabled on the virtual interface of the VLAN, and vice versa.

NOTE:

For more information about the multicast ipv6 routing-enable command, see IP Multicast Command Reference.

Configuring an RP

An RP can be manually configured or dynamically elected through the BSR mechanism. For a large IPv6 PIM network, static RP configuration is a tedious job. Generally, static RP configuration is just a backup means for the dynamic RP election mechanism to enhance the robustness and operation manageability of a multicast network.

Configuring a static RP

If there is only one dynamic RP in a network, manually configuring a static RP can avoid communication interruption due to single-point failures and avoid frequent message exchange between C-RPs and the BSR.

Perform this configuration on all routers in the IPv6 PIM-SM domain.

To configure a static RP:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter IPv6 PIM view.	pim ipv6	N/A
3. Configure a static RP for IPv6 PIM-SM.	static-rp ipv6-rp-address [ acl6-number ] [ preferred ]	No static RP by default

CAUTION:

To enable a static RP to work normally, you must specify the same static RP address on all routers in the IPv6 PIM-SM domain.

Configuring a C-RP

In an IPv6 PIM-SM domain, you can configure routers that intend to become the RP as C-RPs. The BSR collects the C-RP information by receiving the C-RP-Adv messages from C-RPs or auto-RP announcements from other routers and organizes the information into an RP-Set, which is flooded throughout the entire network. Then, the other routers in the network calculate the mappings between specific group ranges and the corresponding RPs based on the RP-Set. We recommend that you configure C-RPs on backbone routers.

To guard against C-RP spoofing, you need to configure a legal C-RP address range and the range of IPv6 multicast groups to be served on the BSR. In addition, because every C-BSR has a chance to become the BSR, you need to configure the same filtering policy on all C-BSRs in the IPv6 PIM-SM domain.

To configure a C-RP:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter IPv6 PIM view.	pim ipv6	N/A
3. Configure an interface to be a C-RP for IPv6 PIM-SM.	c-rp ipv6-address [ { group-policy acl6-number \| scope scope-id } \| priority priority \| holdtime hold-interval \| advertisement-interval adv-interval ] *	No C-RPs are configured by default.
4. Configure a legal C-RP address range and the range of IPv6 multicast groups to be served.	crp-policy acl6-number	Optional. No restrictions by default.

NOTE:

· When you configure a C-RP, ensure a relatively large bandwidth between this C-RP and the other devices in the IPv6 PIM-SM domain.

· An RP can serve multiple IPv6 multicast groups or all IPv6 multicast groups. Only one RP can forward IPv6 multicast traffic for an IPv6 multicast group at a moment.

Enabling embedded RP

With the Embedded RP feature enabled, the router can resolve the RP address directly from the IPv6 multicast group address of an IPv6 multicast packets. This RP can replace the statically configured RP or the RP dynamically calculated based on the BSR mechanism. Thus, the DR does not need to know the RP address beforehand.

Perform this configuration on all routers in the IPv6 PIM-SM domain.

To enable embedded RP:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter IPv6 PIM view.	pim ipv6	N/A
3. Enable embedded RP.	embedded-rp [ acl6-number ]	Optional. By default, embedded RP is enabled for IPv6 multicast groups in the default embedded RP address scopes.

NOTE:

The default embedded RP address scopes are FF7x::/12 and FFFx::/12. Here “x” refers to any legal address scope. For more information about the scope field, see the chapter “Multicast overview.”

Configuring C-RP timers globally

To enable the BSR to distribute the RP-Set information within the IPv6 PIM-SM domain, C-RPs must periodically send C-RP-Adv messages to the BSR. The BSR learns the RP-Set information from the received messages, and encapsulates its own IPv6 address together with the RP-Set information in its bootstrap messages. The BSR then floods the bootstrap messages to all IPv6 routers in the network.

Each C-RP encapsulates a timeout value in its C-RP-Adv message. Upon receiving this message, the BSR obtains this timeout value and starts a C-RP timeout timer. If the BSR fails to hear a subsequent C-RP-Adv message from the C-RP when the timer times out, the BSR assumes the C-RP to have expired or become unreachable.

Perform this configuration on C-RP routers.

To configure C-RP timers globally:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter IPv6 PIM view.	pim ipv6	N/A
3. Configure the C-RP-Adv interval.	c-rp advertisement-interval interval	Optional 60 seconds by default
4. Configure C-RP timeout time.	c-rp holdtime interval	Optional 150 seconds by default

NOTE:

For more information about the configuration of other timers in IPv6 PIM-SM, see “Configuring the prune delay.”

Configuring a BSR

An IPv6 PIM-SM domain can have only one BSR, but must have at least one C-BSR. Any router can be configured as a C-BSR. Elected from C-BSRs, the BSR is responsible for collecting and advertising RP information in the IPv6 PIM-SM domain.

Configuring a C-BSR

C-BSRs should be configured on routers in the backbone network. When you configure a router as a C-BSR, make sure to specify the IPv6 address of an IPv6 PIM-SM enabled interface on the router. The BSR election process is summarized as follows:

· Initially, every C-BSR assumes itself to be the BSR of this IPv6 PIM-SM domain, and uses its interface IPv6 address as the BSR address to send bootstrap messages.

· When a C-BSR receives the bootstrap message of another C-BSR, it first compares its own priority with the other C-BSR’s priority carried in the message. The C-BSR with a higher priority wins. If there is a tie in the priority, the C-BSR with a higher IPv6 address wins. The loser uses the winner’s BSR address to replace its own BSR address and no longer assumes itself to be the BSR, while the winner keeps its own BSR address and continues assuming itself to be the BSR.

Configuring a legal range of BSR addresses enables filtering of bootstrap messages based on the address range, thus to prevent a maliciously configured host from masquerading as a BSR. The same configuration needs to be made on all routers in the IPv6 PIM-SM domain. The following are typical BSR spoofing cases and the corresponding preventive measures:

1. Some maliciously configured hosts can forge bootstrap messages to fool routers and change RP mappings. Such attacks often occur on border routers. Because a BSR is inside the network whereas hosts are outside the network, you can protect a BSR against attacks from external hosts by enabling the border routers to perform neighbor checks and RPF checks on bootstrap messages and discard unwanted messages.

2. When a router in the network is controlled by an attacker or when an illegal router is present in the network, the attacker can configure this router as a C-BSR and make it win BSR election to control the right of advertising RP information in the network. After being configured as a C-BSR, a router automatically floods the network with bootstrap messages. As a bootstrap message has a hop limit value of 1, the whole network is not affected as long as the neighbor router discards these bootstrap messages. Therefore, with a legal BSR address range configured on all routers in the entire network, all these routers discards bootstrap messages from out of the legal address range.

The above-mentioned preventive measures can partially protect the security of BSRs in a network. However, if a legal BSR is controlled by an attacker, the above-mentioned problem also occurs.

To complete basic BSR configuration:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter IPv6 PIM view.	pim ipv6	N/A
3. Configure an interface as a C-BSR.	c-bsr ipv6-address [ hash-length [ priority ] ]	No C-BSRs are configured by default.
4. Configure a legal BSR address range.	bsr-policy acl6-number	Optional. No restrictions by default.

NOTE:

Since a large amount of information needs to be exchanged between a BSR and the other devices in the IPv6 PIM-SM domain, a relatively large bandwidth should be provided between the C-BSR and the other devices in the IPv6 PIM-SM domain.

Configuring an IPv6 PIM domain border

As the administrative core of an IPv6 PIM-SM domain, the BSR sends the collected RP-Set information in the form of bootstrap messages to all routers in the IPv6 PIM-SM domain.

An IPv6 PIM domain border is a bootstrap message boundary. Each BSR has its specific service scope. A number of IPv6 PIM domain border interfaces partition a network into different IPv6 PIM-SM domains. Bootstrap messages cannot cross a domain border in either direction.

Perform the following configuration on routers that you want to configure as an IPv6 PIM domain border.

To configure an IPv6 PIM border domain:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter interface view.	interface interface-type interface-number	N/A
3. Configuring an IPv6 PIM domain border.	pim ipv6 bsr-boundary	No IPv6 PIM domain border is configured by default.

Configuring C-BSR parameters globally

In each IPv6 PIM-SM domain, a unique BSR is elected from C-BSRs. The C-RPs in the IPv6 PIM-SM domain send advertisement messages to the BSR. The BSR summarizes the advertisement messages to form an RP-set and advertises it to all routers in the IPv6 PIM-SM domain. All the routers use the same Hash algorithm to get the RP address corresponding to specific IPv6 multicast groups.

Perform the following configuration on C-BSR routers.

To configure C-BSR parameters globally:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter IPv6 PIM view.	pim ipv6	N/A
3. Configure the Hash mask length.	c-bsr hash-length hash-length	Optional 126 by default
4. Configure the C-BSR priority.	c-bsr priority priority	Optional 64 by default

Configuring C-BSR timers

The BSR election winner multicasts its own IPv6 address and RP-Set information throughout the region that it serves through bootstrap messages. The BSR floods bootstrap messages throughout the network at the interval of BS (BSR state) period. Any C-BSR that receives a bootstrap message retains the RP-set for the length of BS timeout, during which no BSR election takes place. If the BSR state times out and no bootstrap message is received from the BSR, a new BSR election process is triggered among the C-BSRs.

Perform the following configuration on C-BSR routers.

To configure C-BSR timers:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter IPv6 PIM view.	pim ipv6	N/A
3. Configure the BS period.	c-bsr interval interval	Optional. For the default value, see the note below.
4. Configure the BS timeout.	c-bsr holdtime interval	Optional. For the default value, see the note below.

NOTE:

About the BS period:

· By default, the BS period is determined by this formula: BS period = (BS timeout – 10) / 2. The default BS timeout is 130 seconds, so the default BS period = (130 – 10) / 2 = 60 (seconds).

· If this parameter is manually configured, the system uses the configured value.

About the BS timeout:

· By default, the BS timeout value is determined by this formula: BS timeout = BS period × 2 + 10. The default BS period is 60 seconds, so the default BS timeout = 60 × 2 + 10 = 130 (seconds).

· If this parameter is manually configured, the system uses the configured value.

CAUTION:

Be sure to configure a BS period smaller than the BS timeout value.

Disabling BSM semantic fragmentation

Generally, a BSR periodically distributes the RP-set information in bootstrap messages within the IPv6 PIM-SM domain. It encapsulates a BSM in an IPv6 datagram and may split the datagram into fragments if the message exceeds the maximum transmission unit (MTU). In respect of such IP fragmentation, loss of a single IP fragment leads to unavailability of the entire message.

Semantic fragmentation of BSMs can solve this issue. When a BSM exceeds the MTU, it is split to multiple bootstrap message fragments (BSMFs).

· Upon receiving a BSMF that contains the RP-set information of one group range, a non-BSR router updates corresponding RP-set information directly.

· If the RP-set information of one group range is carried in multiple BSMFs, a non-BSR router updates corresponding RP-set information upon receiving all these BSMFs.

Because the RP-set information contained in each segment is different, loss of some IP fragments does not result in dropping of the entire message.

The function of BSM semantic fragmentation is enabled by default. Devices not supporting this function may deem a fragment as an entire message, thus learning only part of the RP-set information. Therefore, if such devices exist in the IPv6 PIM-SM domain, you need to disable the semantic fragmentation function on the C-BSRs.

To disable the BSM semantic fragmentation function:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter IPv6 PIM view.	pim ipv6	N/A
3. Disable the BSM semantic fragmentation function.	undo bsm-fragment enable	By default, the BSM semantic fragmentation function is enabled.

NOTE:

Generally, a BSR performs BSM semantic fragmentation according to the MTU of its BSR interface. However, the semantic fragmentation of BSMs originated due to learning of a new IPv6 PIM neighbor is performed according to the MTU of the outgoing interface.

Configuring IPv6 administrative scoping

With IPv6 administrative scoping disabled, an IPv6 PIM-SM domain has only one BSR. The BSR manages the whole network. To manage your network more effectively and specifically, you can partition the IPv6 PIM-SM domain into multiple IPv6 admin-scope zones. Each IPv6 admin-scope zone maintains a BSR, which serves a specific IPv6 multicast group range; while the IPv6 global scope zone also maintains a BSR, which serves the IPv6 multicast groups with the Scope field in the group addresses being 14.

Enabling IPv6 administrative scoping

Before configuring an IPv6 admin-scope zone, you must enable IPv6 administrative scoping first.

Perform the following configuration on all routers in the IPv6 PIM-SM domain.

To enable IPv6 administrative scoping:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter IPv6 PIM view.	pim ipv6	N/A
3. Enable IPv6 administrative scoping.	c-bsr admin-scope	Disabled by default

Configuring an IPv6 admin-scope zone boundary

The boundary of each IPv6 admin-scope zone is formed by ZBRs. Each admin-scope zone maintains a BSR, which serves multicast groups with a specific Scope field in their group addresses. Multicast protocol packets (such as assert messages and bootstrap messages) that belong to this range cannot cross the admin-scope zone boundary.

Perform the following configuration on routers that you want to configure as a ZBR.

To configure an IPv6 admin-scope zone boundary:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter interface view.	interface interface-type interface-number	N/A
3. Configure an IPv6 multicast forwarding boundary.	multicast ipv6 boundary { ipv6-group-address prefix-length \| scope { scope-id \| admin-local \| global \| organization-local \| site-local } }	By default, no multicast forwarding boundary is configured.

NOTE:

For more information about the multicast ipv6 boundary command, see IP Multicast Command Reference.

Configuring C-BSRs for IPv6 admin-scope zones

In a network with IPv6 administrative scoping enabled, BSRs are elected from C-BSRs specific to different Scope field values. C-RPs in the network send advertisement messages to the specific BSR. The BSR summarizes the advertisement messages to form an RP-set and advertises it to all routers in the specific admin-scope zone. All the routers use the same Hash algorithm to get the RP address corresponding to the specific IPv6 multicast group.

Perform the following configuration on the routers that you want to configure as C-BSRs in IPv6 admin-scope zones.

To configure a C-BSR for an IPv6 admin-scope zone:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter IPv6 PIM view.	pim ipv6	N/A
3. Configure a C-BSR for an IPv6 admin-scope zone.	c-bsr scope { scope-id \| admin-local \| global \| organization-local \| site-local } [ hash-length hash-length \| priority priority ] *	No C-BSRs are configured for an IPv6 admin-scope zone by default.

NOTE:

You can configure the Hash mask length and C-BSR priority globally and/or in an IPv6 admin-scope zone.

· The values configured in the IPv6 admin-scope zone have preference over the global values.

· If you do not configure these parameters in the IPv6 admin-scope zone, the corresponding global values is used.

For configuration of global C-BSR parameters, see “Configuring C-BSR parameters globally.”

Configuring IPv6 multicast source registration

Within an IPv6 PIM-SM domain, the source-side DR sends register messages to the RP, and these register messages have different IPv6 multicast source or IPv6 multicast group addresses. You can configure a filtering rule to filter register messages so that the RP can serve specific IPv6 multicast groups. If an (S, G) entry is denied by the filtering rule, or the action for this entry is not defined in the filtering rule, the RP sends a register-stop message to the DR to stop the registration process for the IPv6 multicast data.

In view of information integrity of register messages in the transmission process, you can configure the device to calculate the checksum based on the entire register messages. However, to reduce the workload of encapsulating data in register messages and for the sake of interoperability, this method of checksum calculation is not recommended.

When receivers stop receiving data addressed to a certain IPv6 multicast group through the RP (that is, the RP stops serving the receivers of that IPv6 multicast group), or when the RP formally starts receiving IPv6 multicast data from the IPv6 multicast source, the RP sends a register-stop message to the source-side DR. Upon receiving this message, the DR stops sending register messages encapsulated with IPv6 multicast data and starts a register-stop timer. When the register-stop timer expires, the DR sends a null register message (a register message without encapsulated multicast data) to the RP. If the DR receives a register-stop message during the register probe time, it resets its register-stop timer. Otherwise, the DR starts sending register messages with encapsulated data again when the register-stop timer expires.

The Register-Stop Timer is set to a random value chosen uniformly from the interval (0.5 times register_suppression_time, 1.5 times register_suppression_time) minus register_probe_time.

Configure a filtering rule for register messages on C-RP routers and configure them to calculate the checksum based on the entire register messages. Configure the register suppression time and the register probe time on routers that may become IPv6 source-side DRs.

To configure register-related parameters:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter IPv6 PIM view.	pim ipv6	N/A
3. Configure a filtering rule for register messages.	register-policy acl6-number	Optional No register filtering rule by default
4. Configure the device to calculate the checksum based on the entire register messages.	register-whole-checksum	Optional Based on the header of register messages by default
5. Configure the register suppression time.	register-suppression-timeout interval	Optional 60 seconds by default
6. Configure the register probe time.	probe-interval interval	Optional 5 seconds by default

Configuring SPT switchover

Because an RPT is possibly not the tree that has the shortest path, the IPv6 multicast forwarding path needs to be switched from the RPT to the SPT when the IPv6 multicast traffic is large. By default, the device switches to the SPT immediately after it receives the first IPv6 multicast packet from the RPT.

CAUTION:

Once a multicast forwarding entry is created on the source-side DR, it stops forwarding subsequent multicast packets in register messages even if a register outgoing interface is available. Therefore, to avoid forwarding failure, do not include the infinity keyword in this command on a static RP or a C-RP.

Perform the following configuration on routers that may become receiver-side DRs.

To configure the device not to initiate an RPT-to-SPT switchover:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter IPv6 PIM view.	pim ipv6	N/A
3. Configure the SPT switchover.	spt-switch-threshold infinity [ group-policy acl6-number [ order order-value ] ]	Optional. By default, the device switches to the SPT immediately after it receives the first IPv6 multicast packet from the RPT.

Configuring IPv6 BIDIR-PIM

IPv6 BIDIR-PIM configuration task list

Complete these tasks to configure IPv6 BIDIR-PIM:

Task		Remarks
Enabling IPv6 PIM-SM		Required.
Enabling IPv6 BIDIR-PIM		Required.
Configuring an RP	Configuring a static RP	Required. Use any approach.
	Configuring a C-RP
	Enabling embedded RP
	Configuring C-RP timers globally	Optional.
Configuring a BSR	Configuring a C-BSR	Required.
	Configuring an IPv6 BIDIR-PIM domain border	Optional.
	Configuring global C-BSR parameters	Optional.
	Configuring C-BSR timers	Optional.
	Disabling BSM semantic fragmentation	Optional.
Configuring IPv6 administrative scoping	Enabling IPv6 administrative scoping	Optional.
	Configuring an IPv6 admin-scope zone boundary	Optional.
	Configuring C-BSRs for each admin-scope zone	Optional.
Configuring IPv6 PIM common features		Optional

Configuration prerequisites

Before configuring IPv6 BIDIR-PIM, complete the following task:

· Enable IPv6 forwarding and configure an IPv6 unicast routing protocol so that all devices in the domain can communicate with each other at Layer 3.

· Determine the IPv6 address of a static RP and the IPv6 ACL that defines the range of IPv6 multicast groups to be served by the static RP.

· Determine the C-RP priority and the IPv6 ACL that defines the range of IPv6 multicast groups to be served by each C-RP.

· Determine the legal C-RP address range and the IPv6 ACL that defines the range of IPv6 multicast groups to be served.

· Determine the C-RP-Adv interval.

· Determine the C-RP timeout.

· Determine the C-BSR priority.

· Determine the hash mask length.

· Determine the IPv6 ACL that defines the legal BSR address range.

· Determine the BS period.

· Determine the BS timeout timer.

Enabling IPv6 PIM-SM

You must enable IPv6 PIM-SM before enabling IPv6 BIDIR-PIM because IPv6 BIDIR-PIM is implemented on the basis of IPv6 PIM-SM. To deploy an IPv6 BIDIR-PIM domain, enable IPv6 PIM-SM on all non-border interfaces of the domain.

To enable IPv6 PIM-SM:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enable IPv6 multicast routing.	multicast ipv6 routing-enable	Disable by default
3. Enter interface view.	interface interface-type interface-number	N/A
4. Enable IPv6 PIM-SM.	pim ipv6 sm	Disabled by default

CAUTION:

On a router, all interfaces in the same VPN instance must work in the same IPv6 PIM mode.

NOTE:

For more information about the multicast ipv6 routing-enable command, see IP Multicast Command Reference.

Enabling IPv6 BIDIR-PIM

NOTE:

· The router supports IPv6 BIDIR-PIM only when it works in SPE mode. For more information about system working mode, see Fundamentals Configuration Guide.

· If BIDIR-PIM is enabled on the public network or in a VPN, the tunnel interfaces on the public network or in the VPN do not support Layer 3 multicasting.

Perform this configuration on all routers in the IPv6 BIDIR-PIM domain.

To enable IPv6 BIDIR-PIM:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter IPv6 PIM view.	pim ipv6	N/A
3. Enable IPv6 BIDIR-PIM.	bidir-pim enable	Disabled by default

Configuring an RP

Configuring a static RP

Perform this configuration on all routers in the IPv6 BIDIR-PIM domain.

To configure a static RP:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter IPv6 PIM view.	pim ipv6	N/A
3. Configure a static RP for IPv6 BIDIR-PIM.	static-rp ipv6-rp-address [ acl6-number ] [ preferred ] bidir	No static RP by default

CAUTION:

You must perform static RP configuration on all routers in the IPv6 PIM-SM domain and specify the same RP address.

NOTE:

In IPv6 BIDIR-PIM, a static RP can be specified with a virtual IPv6 address. For example, if the IPv6 addresses of the interfaces at the two ends of a link are 1001::1/64 and 1001::2/64, you can specify a virtual IPv6 address, like 1001::100/64, for the static RP. As a result, the link becomes an RPL.

Configuring a C-RP

In an IPv6 BIDIR-PIM domain, you can configure routers that intend to become the RP as C-RPs. The BSR collects the C-RP information by receiving the C-RP-Adv messages from C-RPs or auto-RP announcements from other routers and organizes the information into an RP-set, which is flooded throughout the entire network. Then, the other routers in the network calculate the mappings between specific group ranges and the corresponding RPs based on the RP-set. H3C recommends that you configure C-RPs on backbone routers.

To guard against C-RP spoofing, configure a legal C-RP address range and the range of multicast groups to be served on the BSR. In addition, because every C-BSR has a chance to become the BSR, you must configure the same filtering policy on all C-BSRs in the IPv6 BIDIR-PIM domain.

To configure a C-RP:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter IPv6 PIM view.	pim ipv6	N/A
3. Configure an interface to be a C-RP for IPv6 BIDIR-PIM.	c-rp ipv6-address [ { group-policy acl6-number \| scope scope-id } \| priority priority \| holdtime hold-interval \| advertisement-interval adv-interval ] * bidir	No C-RP is configured by default.

NOTE:

· When you configure a C-RP, ensure a relatively large bandwidth between this C-RP and the other devices in the IPv6 BIDIR-PIM domain.

· An RP can serve multiple IPv6 multicast groups or all IPv6 multicast groups. Only one RP can forward multicast traffic for an IPv6 multicast group at a moment.

Enabling embedded RP

With the embedded RP feature enabled, the router can resolve the RP address directly from the IPv6 multicast group address of an IPv6 multicast packets. This RP can replace the statically configured RP or the RP dynamically calculated based on the BSR mechanism. Thus, the DR does not need to know the RP address beforehand.

Perform this configuration on all routers in the BIDIR-PIM domain.

To enable embedded RP:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter IPv6 PIM view.	pim ipv6	N/A
3. Enable embedded RP.	embedded-rp [ acl6-number ]	Optional. By default, embedded RP is enabled for IPv6 multicast groups in the default embedded RP address scopes.

NOTE:

The default embedded RP address scopes are FF7x::/12 and FFFx::/12, where x refers to any legal address scope. For more information about the Scope field, see the chapter “Multicast overview.”

Configuring C-RP timers globally

To enable the BSR to distribute the RP-Set information within the IPv6 BIDIR-PIM domain, C-RPs must periodically send C-RP-Adv messages to the BSR. The BSR learns the RP-Set information from the received messages, and encapsulates its own IPv6 address together with the RP-Set information in its bootstrap messages. The BSR then floods the bootstrap messages to all IPv6 routers in the network.

Each C-RP encapsulates a timeout value in its C-RP-Adv messages. Upon receiving a C-RP-Adv message, the BSR obtains this timeout value and starts a C-RP timeout timer. If the BSR fails to hear a subsequent C-RP-Adv message from the C-RP when the timer times out, the BSR assumes the C-RP to have expired or become unreachable.

The C-RP timers need to be configured on C-RP routers.

To configure C-RP timers globally:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter IPv6 PIM view.	pim ipv6	N/A
3. Configure the C-RP-Adv interval.	c-rp advertisement-interval interval	Optional 60 seconds by default
4. Configure C-RP timeout time.	c-rp holdtime interval	Optional 150 seconds by default

NOTE:

For more information about the configuration of other timers in IPv6 PIM-SM, see “Configuring IPv6 PIM common timers.”

Configuring a BSR

An IPv6 BIDIR-PIM domain can have only one BSR, but must have at least one C-BSR. Any router can be configured as a C-BSR. Elected from C-BSRs, the BSR collects and advertises RP information in the IPv6 BIDIR-PIM domain.

Configuring a C-BSR

C-BSRs must be configured on routers on the backbone network. When you configure a router as a C-BSR, be sure to specify an IPv6 PIM-SM-enabled interface on the router. The BSR election process is as follows:

· Initially, every C-BSR assumes itself to be the BSR of the IPv6 BIDIR-PIM domain, and uses its interface IPv6 address as the BSR address to send bootstrap messages.

· When a C-BSR receives the bootstrap message of another C-BSR, it first compares its own priority with the other C-BSR’s priority carried in message. The C-BSR with a higher priority wins. If there is a tie in the priority, the C-BSR with a higher IPv6 address wins. The loser uses the winner’s BSR address to replace its own BSR address and no longer assumes itself to be the BSR, while the winner retains its own BSR address and continues assuming itself to be the BSR.

Configuring a legal range of BSR addresses enables filtering of bootstrap messages based on the address range, thus to prevent a maliciously configured host from masquerading as a BSR. The same configuration must be made on all routers in the IPv6 BIDIR-PIM domain. The following are typical BSR spoofing cases and the corresponding preventive measures:

2. When a router in the network is controlled by an attacker or when an illegal router is present in the network, the attacker can configure this router as a C-BSR and make it win BSR election to control the right of advertising RP information in the network. After being configured as a C-BSR, a router automatically floods the network with bootstrap messages. Because a bootstrap message has a hop limit value of 1, the whole network is not affected as long as the neighbor router discards these bootstrap messages. Therefore, with a legal BSR address range configured on all routers in the entire network, all these routers discards bootstrap messages from out of the legal address range.

The above-mentioned preventive measures can partially protect the security of BSRs in a network. However, if a legal BSR is controlled by an attacker, the above-mentioned problem still occurs.

To configure a C-BSR:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter IPv6 PIM view.	pim ipv6	N/A
3. Configure an interface as a C-BSR.	c-bsr ipv6-address [ hash-length [ priority ] ]	No C-BSRs are configured by default.
4. Configure a legal BSR address range.	bsr-policy acl6-number	Optional. No restrictions on BSR address range by default.

NOTE:

Because a large amount of information is to be exchanged between a BSR and the other devices in the IPv6 BIDIR-PIM domain, a relatively large bandwidth should be provided between the C-BSRs and the other devices in the IPv6 BIDIR-PIM domain.

Configuring an IPv6 BIDIR-PIM domain border

As the administrative core of an IPv6 BIDIR-PIM domain, the BSR sends the collected RP-Set information in the form of bootstrap messages to all routers in the IPv6 BIDIR-PIM domain.

An IPv6 BIDIR-PIM domain border is a bootstrap message boundary. Each BSR has its specific service scope. A number of IPv6 BIDIR-PIM domain border interfaces partition a network into different IPv6 BIDIR-PIM domains. Bootstrap messages cannot cross a domain border in either direction.

Perform the following configuration on routers that you want to configure as the IPv6 BIDIR-PIM domain border.

To configure an IPv6 BIDIR-PIM domain border:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter interface view.	interface interface-type interface-number	N/A
3. Configure an IPv6 BIDIR-PIM domain border.	pim ipv6 bsr-boundary	By default, no IPv6 BIDIR-PIM domain border is configured.

Configuring global C-BSR parameters

In each IPv6 BIDIR-PIM domain, a unique BSR is elected from C-BSRs. The C-RPs in the IPv6 BIDIR-PIM domain send advertisement messages to the BSR. The BSR summarizes the advertisement messages to form an RP-set and advertises it to all routers in the IPv6 BIDIR-PIM domain. All the routers use the same Hash algorithm to get the RP address corresponding to specific multicast groups.

Perform the following configuration on C-BSR routers.

To configure global C-BSR parameters:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter IPv6 PIM view.	pim ipv6	N/A
3. Configure the Hash mask length.	c-bsr hash-length hash-length	Optional 126 by default
4. Configure the C-BSR priority.	c-bsr priority priority	Optional 64 by default

Configuring C-BSR timers

The BSR election winner multicasts its own IPv6 address and RP-Set information through bootstrap messages within the entire zone it serves. The BSR floods bootstrap messages throughout the network at the interval of BS (BSR state) period. Any C-BSR that receives a bootstrap message retains the RP-set for the length of BS timeout, during which no BSR election takes place. If the BSR state times out and no bootstrap message is received from the BSR, a new BSR election process is triggered among the C-BSRs.

Perform the following configuration on C-BSR routers.

To configure C-BSR timers:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter IPv6 PIM view.	pim ipv6	N/A
3. Configure the BS period.	c-bsr interval interval	Optional. For the default value, see the note below.
4. Configure the BS timeout.	c-bsr holdtime interval	Optional. For the default value, see the note below.

NOTE:

About the BS period:

· By default, the BS period is determined by this formula: BS period = (BS timeout – 10) / 2. The default BS timeout is 130 seconds, so the default BS period = (130 – 10) / 2 = 60 (seconds).

· If this parameter is manually configured, the system uses the configured value.

About the BS timeout:

· By default, the BS timeout value is determined by this formula: BS timeout = BS period × 2 + 10. The default BS period is 60 seconds, so the default BS timeout = 60 × 2 + 10 = 130 (seconds).

· If this parameter is manually configured, the system uses the configured value.

CAUTION:

Be sure to configure a BS period value smaller than the BS timeout value.

Disabling BSM semantic fragmentation

Generally, a BSR periodically distributes the RP-set information in bootstrap messages within the IPv6 BIDIR-PIM domain. It encapsulates a BSM in an IP datagram and may split the datagram into fragments if the message exceeds the maximum transmission unit (MTU). In respect of such IP fragmentation, loss of a single IP fragment leads to unavailability of the entire message.

Semantic fragmentation of BSMs can solve this issue. When a BSM exceeds the MTU, it is split to multiple bootstrap message fragments (BSMFs).

· Upon receiving a BSMF that contains the RP-set information of one group range, a non-BSR router updates corresponding RP-set information directly.

· If the RP-set information of one group range is carried in multiple BSMFs, a non-BSR router updates corresponding RP-set information upon receiving all these BSMFs.

Because the RP-set information contained in each segment is different, loss of some IP fragments does not result in dropping of the entire message.

The function of BSM semantic fragmentation is enabled by default. Devices not supporting this function may deem a fragment as an entire message, thus learning only part of the RP-set information. Therefore, if such devices exist in the IPv6 BIDIR-PIM domain, you need to disable the semantic fragmentation function on the C-BSRs.

To disable the BSM semantic fragmentation function:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter IPv6 PIM view.	pim ipv6	N/A
3. Disable the BSM semantic fragmentation function.	undo bsm-fragment enable	By default, the BSM semantic fragmentation function is enabled.

NOTE:

Generally, a BSR performs BSM semantic fragmentation according to the MTU of its BSR interface. However, the semantic fragmentation of BSMs originated due to learning of a new PIM neighbor is performed according to the MTU of the outgoing interface.

Configuring IPv6 administrative scoping

With administrative scoping disabled, an IPv6 BIDIR-PIM domain has only one BSR. The BSR manages the whole network. To manage your network more effectively and specifically, you can partition the IPv6 BIDIR-PIM domain into multiple admin-scope zones. Each admin-scope zone maintains a BSR, which serves a specific multicast group range; while the global scope zone also maintains a BSR, which serves all the rest multicast groups.

Enabling IPv6 administrative scoping

Before configuring an IPv6 admin-scope zone, you must enable IPv6 administrative scoping first.

Perform the following configuration on all routers in the BIDIR-PIM domain.

To enable IPv6 administrative scoping:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter IPv6 PIM view.	pim ipv6	N/A
3. Enable IPv6 administrative scoping.	c-bsr admin-scope	Disabled by default

Configuring an IPv6 admin-scope zone boundary

The boundary of each IPv6 admin-scope zone is formed by ZBRs. Each admin-scope zone maintains a BSR, which serves a specific IPv6 multicast group range. IPv6 multicast packets (such as assert messages and bootstrap messages) that belong to this range cannot cross the admin-scope zone boundary.

Perform the following configuration on routers that you want to configure as a ZBR.

To configure an admin-scope zone boundary:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter interface view.	interface interface-type interface-number	N/A
3. Configure an IPv6 multicast forwarding boundary.	multicast ipv6 boundary { ipv6-group-address prefix-length \| scope { scope-id \| admin-local \| global \| organization-local \| site-local } }	By default, no IPv6 multicast forwarding boundary is configured.

NOTE:

For more information about the multicast ipv6 boundary command, see IP Multicast Command Reference.

Configuring C-BSRs for each admin-scope zone

In a network with administrative scoping enabled, group-range-specific BSRs are elected from C-BSRs. C-RPs in the network send advertisement messages to the specific BSR. The BSR summarizes the advertisement messages to form an RP-set and advertises it to all routers in the specific admin-scope zone. All the routers use the same Hash algorithm to get the RP address corresponding to the specific multicast group.

Perform the following configuration on the routers that you want to configure as C-BSRs in admin-scope zones.

To configure a C-BSR for an admin-scope zone:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter IPv6 PIM view.	pim ipv6	N/A
3. Configure a C-BSR for an admin-scope zone.	c-bsr scope { scope-id \| admin-local \| global \| organization-local \| site-local } [ hash-length hash-length \| priority priority ] *	No C-BSRs are configured for an admin-scope zone by default.

NOTE:

You can configure the Hash mask length and C-BSR priority globally and/or in an IPv6 admin-scope zone.

· The values configured in the IPv6 admin-scope zone have preference over the global values.

· If you do not configure these parameters in the IPv6 admin-scope zone, the corresponding global values is used.

For configuration of global C-BSR parameters, see “Configuring global C-BSR parameters.”

Configuring IPv6 PIM-SSM

NOTE:

The IPv6 PIM-SSM model needs the support of MLDv2. Therefore, be sure to enable MLDv2 on IPv6 PIM routers with receivers attached to them.

IPv6 PIM-SSM configuration task list

Complete these tasks to configure IPv6 PIM-SSM:

Task	Remarks
Enabling IPv6 PIM-SM	Required
Configuring the IPv6 SSM group range	Optional
Configuring IPv6 PIM common features	Optional

Configuration prerequisites

Before configuring IPv6 PIM-SSM, complete the following task:

· Enable IPv6 forwarding and configure any IPv6 unicast routing protocol so that all devices in the domain are interoperable at the network layer.

· Determine the IPv6 SSM group range.

Enabling IPv6 PIM-SM

The SSM model is implemented based on some subsets of IPv6 PIM-SM. Therefore, you must enable IPv6 PIM-SM before configuring IPv6 PIM-SSM.

When you deploy an IPv6 PIM-SM domain, H3C recommends you to enable IPv6 PIM-SM on all non-border interfaces of routers.

To enable IPv6 PIM-SSM:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enable IPv6 multicast routing.	multicast ipv6 routing-enable	Disable by default
3. Enter interface view.	interface interface-type interface-number	N/A
4. Enable IPv6 PIM-SM.	pim ipv6 sm	Disabled by default

CAUTION:

All the interfaces of the same device must work in the same IPv6 PIM mode.

NOTE:

For more information about the multicast ipv6 routing-enable command, see IP Multicast Command Reference.

Configuring the IPv6 SSM group range

As for whether the information from an IPv6 multicast source is delivered to the receivers based on the IPv6 PIM-SSM model or the IPv6 PIM-SM model, this depends on whether the group address in the (S, G) channel subscribed by the receivers falls in the IPv6 SSM group range. All IPv6 PIM-SM-enabled interfaces assume that IPv6 multicast groups within this address range are using the IPv6 SSM model.

Perform the following configuration on all routers in the IPv6 PIM-SM domain.

To configure the IPv6 SSM group range:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter IPv6 PIM view.	pim ipv6	N/A
3. Configure the IPv6 SSM group range.	ssm-policy acl6-number	Optional. FF3x::/32 by default, here “x” refers to any legal group scope.

CAUTION:

· Make sure that the same IPv6 SSM group range is configured on all routers in the entire domain. Otherwise, IPv6 multicast data cannot be delivered through the IPv6 SSM model.

· When a member of an IPv6 multicast group in the IPv6 SSM group range sends an MLDv1 report message, the device does not trigger a (*, G) join.

Configuring IPv6 PIM common features

NOTE:

For the functions or parameters that can be configured in both IPv6 PIM view and interface view described in this section:

· Configurations performed in IPv6 PIM view are effective to all interfaces, while configurations performed in interface view are effective to the current interface only.

· If the same function or parameter is configured in both IPv6 PIM view and interface view, the configuration made in interface view has preference over the configuration made in PIM view, regardless of the configuration sequence.

IPv6 PIM common feature configuration task list

Complete these tasks to configure IPv6 PIM common features:

Task	Remarks
Configuring an IPv6 multicast data filter	Optional
Configuring a hello message filter	Optional
Configuring IPv6 PIM hello options	Optional
Configuring the prune delay	Optional
Configuring IPv6 PIM common timers	Optional
Configuring join/prune message sizes	Optional
Configuring IPv6 PIM to work with BFD	Optional

Configuration prerequisites

Before configuring IPv6 PIM common features, complete the following tasks:

· Enable IPv6 forwarding and configure any IPv6 unicast routing protocol so that all devices in the domain are interoperable at the network layer.

· Configure IPv6 PIM-DM (or IPv6 PIM-SM or IPv6 PIM-SSM).

· Determine the IPv6 ACL for filtering IPv6 multicast data.

· Determine the IPv6 ACL that defines a legal source address range for hello messages.

· Determine the priority for DR election (global value/interface level value).

· Determine the IPv6 PIM neighbor timeout time (global value/interface value).

· Determine the prune message delay (global value/interface level value).

· Determine the prune override interval (global value/interface level value).

· Determine the prune delay.

· Determine the hello interval (global value/interface level value).

· Determine the maximum delay between hello message (interface level value).

· Determine the assert timeout time (global value/interface value).

· Determine the join/prune interval (global value/interface level value).

· Determine the join/prune timeout (global value/interface value).

· Determine the IPv6 multicast source lifetime.

· Determine the maximum size of join/prune messages.

· Determine the maximum number of (S, G) entries in a join/prune message.

Configuring an IPv6 multicast data filter

No matter in an IPv6 PIM-DM domain or an IPv6 PIM-SM domain, routers can check passing-by IPv6 multicast data based on the configured filtering rules and determine whether to continue forwarding the IPv6 multicast data. In other words, IPv6 PIM routers can act as IPv6 multicast data filters. These filters can help implement traffic control on one hand, and control the information available to downstream receivers to enhance data security on the other hand.

To configure an IPv6 multicast data filter:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter IPv6 PIM view.	pim ipv6	N/A
3. Configure an IPv6 multicast group filter.	source-policy acl6-number	No IPv6 multicast data filter by default

NOTE:

· Generally, a smaller distance from the filter to the IPv6 multicast source results in a more remarkable filtering effect.

· This filter works not only on independent IPv6 multicast data but also on IPv6 multicast data encapsulated in register messages.

Configuring a hello message filter

Along with the wide applications of IPv6 PIM, the security requirement for the protocol is becoming more and more demanding. The establishment of correct IPv6 PIM neighboring relationships is a prerequisite for secure application of IPv6 PIM. You can configure a legal source address range for hello messages on interfaces of routers to ensure the correct IPv6 PIM neighboring relationships and thus to guide against IPv6 PIM message attacks.

To configure a hello message filter:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter interface view.	interface interface-type interface-number	N/A
3. Configure a hello message filter.	pim ipv6 neighbor-policy acl6-number	No hello message filter by default

NOTE:

With the hello message filter configured, if hello messages of an existing IPv6 PIM neighbor fail to pass the filter, the IPv6 PIM neighbor is removed automatically when it times out.

Configuring IPv6 PIM hello options

No matter in an IPv6 PIM-DM domain or an IPv6 PIM-SM domain, the hello messages sent among routers contain many configurable options, including:

· DR_Priority (for IPv6 PIM-SM only)—Priority for DR election. The higher the priority is, the easier it is for the router to win DR election. You can configure this parameter on all the routers in a multi-access network directly connected to IPv6 multicast sources or receivers.

· Holdtime—The timeout time of IPv6 PIM neighbor reachability state. When this timer times out, if the router has received no hello message from an IPv6 PIM neighbor, it assumes that this neighbor has expired or become unreachable.

· LAN_Prune_Delay—the delay of prune messages on a multi-access network. This option consists of Lan-delay (namely, prune message delay), Override-interval, and neighbor tracking flag. If the LAN-delay or override-interval values of different IPv6 PIM routers on a multi-access subnet are different, the largest value takes effect. If you want to enable neighbor tracking, the neighbor tracking feature should be enabled on all IPv6 PIM routers on a multi-access subnet.

The LAN-delay setting causes the upstream routers to delay forwarding received prune messages. The override-interval sets the length of time a downstream router is allowed to wait before sending a prune override message. When a router receives a prune message from a downstream router, it does not perform the prune action immediately; instead, it maintains the current forwarding state for a period of LAN-delay plus override-interval. If the downstream router needs to continue receiving IPv6 multicast data, it must send a join message within the prune override interval; otherwise, the upstream route performs the prune action when the period of LAN-delay plus override-interval time out.

A hello message sent from an IPv6 PIM router contains a generation ID option. The generation ID is a random value for the interface on which the hello message is sent. Normally, the generation ID of an IPv6 PIM router does not change unless the status of the router changes (for example, when IPv6 PIM is just enabled on the interface or the device is restarted). When the router starts or restarts sending hello messages, it generates a new generation ID. If an IPv6 PIM router finds that the generation ID in a hello message from the upstream router has changed, it assumes that the status of the upstream neighbor is lost or the upstream neighbor has changed. In this case, it triggers a join message for state update.

If you disable join suppression (namely, enable neighbor tracking), the join suppression feature should be disabled on all IPv6 PIM routers on a multi-access subnet; otherwise, the upstream router fails to explicitly track which downstream routers have joined to it.

Configuring hello options globally

To configure hello options globally:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter IPv6 PIM view.	pim ipv6	N/A
3. Configure the priority for DR election.	hello-option dr-priority priority	Optional 1 by default
4. Configure IPv6 PIM neighbor timeout time.	hello-option holdtime interval	Optional 105 seconds by default
5. Configure the prune message delay time (LAN-delay).	hello-option lan-delay interval	Optional 500 milliseconds by default
6. Configure the prune override interval.	hello-option override-interval interval	Optional 2500 milliseconds by default
7. Disable join suppression.	hello-option neighbor-tracking	Enabled by default

Configuring hello options on an interface

To configure hello options on an interface:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter interface view.	interface interface-type interface-number	N/A
3. Configure the priority for DR election.	pim ipv6 hello-option dr-priority priority	Optional. 1 by default.
4. Configure IPv6 PIM neighbor timeout time.	pim ipv6 hello-option holdtime interval	Optional. 105 seconds by default.
5. Configure the prune message delay time (LAN-delay).	pim ipv6 hello-option lan-delay interval	Optional. 500 milliseconds by default.
6. Configure the prune override interval.	pim ipv6 hello-option override-interval interval	Optional. 2500 milliseconds by default.
7. Disable join suppression.	pim ipv6 hello-option neighbor-tracking	Enabled by default.
8. Configure the interface to reject hello messages without a generation ID.	pim ipv6 require-genid	By default, hello messages without Generation_ID are accepted.

Configuring the prune delay

If a downstream router on a multi-access LAN does not support the prune override interval option, you can configure the prune delay time on the upstream router so that it does not perform the prune action immediately after receiving the prune message; instead, it maintains the current forwarding state for a period of prune delay time. In this period, if the upstream router receives a join message from the downstream router, it cancels the prune action.

To configure the prune delay time

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter IPv6 PIM view.	pim ipv6	N/A
3. Configure the prune delay interval.	prune delay interval	Optional. The prune delay time equals to the prune pending time, which is 3 seconds by default.

Configuring IPv6 PIM common timers

IPv6 PIM routers discover IPv6 PIM neighbors and maintain IPv6 PIM neighboring relationships with other routers by periodically sending out hello messages.

Upon receiving a hello message, an IPv6 PIM router waits a random period, which is equal to or smaller than the maximum delay between hello messages, before sending a hello message. This avoids collisions that occur when multiple IPv6 PIM routers send hello messages simultaneously.

An IPv6 PIM router periodically sends join/prune messages to its upstream for state update. A join/prune message contains the join/prune timeout time. The upstream router sets a join/prune timeout timer for each pruned downstream interface.

Any router that has lost assert election prunes its downstream interface and maintain the assert state for a period of time. When the assert state times out, the assert losers resume IPv6 multicast forwarding.

When a router fails to receive subsequent IPv6 multicast data from the IPv6 multicast source S, the router does not immediately delete the corresponding (S, G) entry; instead, it maintains the (S, G) entry for a period of time, namely the IPv6 multicast source lifetime, before deleting the (S, G) entry.

Configuring IPv6 PIM common timers globally

To configure IPv6 PIM common timers globally:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter IPv6 PIM view.	pim ipv6	N/A
3. Configure the hello interval.	timer hello interval	Optional. 30 seconds by default
4. Configure the join/prune interval.	timer join-prune interval	Optional. 60 seconds by default
5. Configure assert timeout time.	holdtime assert interval	Optional 180 seconds by default
6. Configure the join/prune timeout time.	holdtime join-prune interval	Optional 210 seconds by default
7. Configure the IPv6 multicast source lifetime.	source-lifetime interval	Optional 210 seconds by default

Configuring IPv6 PIM common timers on an interface

To configure IPv6 PIM common timers on an interface:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter interface view.	interface interface-type interface-number	N/A
3. Configure the hello interval.	pim ipv6 timer hello interval	Optional 30 seconds by default
4. Configure the maximum delay between hello messages.	pim ipv6 triggered-hello-delay interval	Optional 5 seconds by default
5. Configure the join/prune interval.	pim ipv6 timer join-prune interval	Optional 60 seconds by default
6. Configure assert timeout time.	pim ipv6 holdtime assert interval	Optional 180 seconds by default
7. Configure the join/prune timeout time.	pim ipv6 holdtime join-prune interval	Optional 210 seconds by default

NOTE:

If there are no special networking requirements, we recommend that you use the default settings.

Configuring join/prune message sizes

A larger join/prune message size results in loss of a larger amount of information when a message is lost; with a reduced join/message size, the loss of a single message brings relatively minor impact.

By controlling the maximum number of (S, G) entries in a join/prune message, you can effectively reduce the number of (S, G) entries sent per unit of time.

To configure join/prune message sizes:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter IPv6 PIM view.	pim ipv6	N/A
3. Configure the maximum size of a join/prune message.	jp-pkt-size packet-size	Optional 8100 bytes by default
4. Configure the maximum number of (S, G) entries in a join/prune message.	jp-queue-size queue-size	Optional 1020 by default

Configuring IPv6 PIM to work with BFD

IPv6 PIM uses hello messages to elect a DR for a multi-access network. The elected DR will be the only multicast forwarder on the multi-access network.

If the DR fails, a new DR election process will start after the DR is aged out. However, it might take a long period of time. To start a new DR election process immediately after the origianl DR fails, you can enable IPv6 PIM to work with Bidirectional Forwarding Detection (BFD) on a multi-access network to detect failures of the links among IPv6 PIM neighbors. You must enable IPv6 PIM to work with BFD on all IPv6 PIM-capable routers on a multi-access network, so that the IPv6 PIM neighbors can fast detect DR failures and start a new DR election process.

Before you configure this feature on an interface, be sure to enable IPv6 PIM-DM or IPv6 PIM-SM on the interface.

To enable IPv6 PIM to work with BFD:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter interface view.	interface interface-type interface-number	N/A
3. Enable IPv6 PIM to work with BFD.	pim ipv6 bfd enable	Disabled by default

NOTE:

For more information about BFD, see High Availability Configuration Guide.

Displaying and maintaining IPv6 PIM

Task	Command	Remarks
1. Display BSR information in the IPv6 PIM-SM domain and locally configured C-RP information in effect.	display pim ipv6 bsr-info [ \| { begin \| exclude \| include } regular-expression ]	Available in any view
2. Display IPv6 unicast routes used by IPv6 PIM.	display pim ipv6 claimed-route [ ipv6-source-address ] [ \| { begin \| exclude \| include } regular-expression ]	Available in any view
3. Display the number of IPv6 PIM control messages.	display pim ipv6 control-message counters [ message-type { probe \| register \| register-stop } \| [ interface interface-type interface-number \| message-type { assert \| bsr \| crp \| graft \| graft-ack \| hello \| join-prune \| state-refresh } ] * ] [ \| { begin \| exclude \| include } regular-expression ]	Available in any view
4. Display the DF information of IPv6 BIDIR-PIM.	display pim ipv6 df-info [ rp-address ] [ \| { begin \| exclude \| include } regular-expression ]	Available in any view
5. Display information about unacknowledged graft messages.	display pim ipv6 grafts [ \| { begin \| exclude \| include } regular-expression ]	Available in any view
6. Display IPv6 PIM information on an interface.	display pim ipv6 interface [ interface-type interface-number ] [ verbose ] [ \| { begin \| exclude \| include } regular-expression ]	Available in any view
7. Display information about join/prune messages to send.	display pim ipv6 join-prune mode { sm [ flags flag-value ] \| ssm } [ interface interface-type interface-number \| neighbor ipv6-neighbor-address ] * [ verbose ] [ \| { begin \| exclude \| include } regular-expression ]	Available in any view
8. Display IPv6 PIM neighboring information.	display pim ipv6 neighbor [ interface interface-type interface-number \| ipv6-neighbor-address \| verbose ] * [ \| { begin \| exclude \| include } regular-expression ]	Available in any view
9. Display IPv6 PIM routing table.	display pim ipv6 routing-table [ ipv6-group-address [ prefix-length ] \| ipv6-source-address [ prefix-length ] \| incoming-interface [ interface-type interface-number \| register ] \| outgoing-interface { include \| exclude \| match } { interface-type interface-number \| register } \| mode mode-type \| flags flag-value \| fsm ] * [ \| { begin \| exclude \| include } regular-expression ]	Available in any view
10. Display RP information.	display pim ipv6 rp-info [ ipv6-group-address ] [ \| { begin \| exclude \| include } regular-expression ]	Available in any view
11. Clear statistics for IPv6 PIM control messages.	reset pim ipv6 control-message counters [ interface interface-type interface-number ]	Available in user view

IPv6 PIM configuration examples

IPv6 PIM-DM configuration example

Network requirements

Receivers receive VOD information through multicast. The receiver groups of different organizations form stub networks, and at least one receiver host exists in each stub network. The entire IPv6 PIM domain operates in the dense mode.

Host A and Host C are IPv6 multicast receivers in two stub networks N1 and N2.

MLDv1 runs between Router A and N1 and between Router B/Router C and N2.

Figure 14 Network diagram

Device	Interface	IP address	Device	Interface	IP address
Router A	GE3/1/1	1001::1/64	Router D	GE3/1/1	4001::1/64
	S4/1/9/1:0	1002::1/64		S4/1/9/1:0	1002::2/64
Router B	GE3/1/1	2001::1/64		POS5/1/1	2002::2/64
	POS5/1/1	2002::1/64		POS5/1/2	3001::2/64
Router C	GE3/1/1	2001::2/64
	POS5/1/1	3001::1/64

Configuration procedure

1. Enable IPv6 forwarding, assign IPv6 addresses, and configure IPv6 unicast routing:

Enable IPv6 forwarding and configure the IP address and prefix length for each interface as per Figure 14. (Details not shown)

Configure the OSPFv3 protocol for interoperation among the routers in the IPv6 PIM-DM domain. Ensure the network-layer interoperation in the IPv6 PIM-DM domain and enable dynamic update of routing information among the routers through an IPv6 unicast routing protocol. (Details not shown)

2. Enable IPv6 multicast routing, IPv6 PIM-DM, and MLD:

# Enable IPv6 multicast routing on Router A, and enable IPv6 PIM-DM on each interface and enable MLD on GigabitEthernet 3/1/1, which connects Router A to N1.

<RouterA> system-view

[RouterA] multicast ipv6 routing-enable

[RouterA] interface GigabitEthernet 3/1/1

[RouterA-GigabitEthernet3/1/1] mld enable

[RouterA-GigabitEthernet3/1/1] pim ipv6 dm

[RouterA-GigabitEthernet3/1/1] quit

[RouterA] interface Serial4/1/9/1:0

[RouterA-Serial4/1/9/1:0] pim ipv6 dm

[RouterA-Serial4/1/9/1:0] quit

The configuration on Router B and Router C is similar to that on Router A.

# Enable IPv6 multicast routing on Router D, and enable IPv6 PIM-DM on each interface.

<RouterD> system-view

[RouterD] multicast ipv6 routing-enable

[RouterD] interface GigabitEthernet 3/1/1

[RouterD-GigabitEthernet3/1/1] pim ipv6 dm

[RouterD-GigabitEthernet3/1/1] quit

[RouterD] interface Serial 4/1/9/1:0

[RouterD-Serial4/1/9/1:0] pim ipv6 dm

[RouterD-Serial4/1/9/1:0] quit

[RouterD] interface pos 5/1/1

[RouterD-Pos5/1/1] pim ipv6 dm

[RouterD-Pos5/1/1] quit

[RouterD] interface pos 5/1/2

[RouterD-Pos5/1/2] pim ipv6 dm

[RouterD-Pos5/2/2] quit

3. Verify the configuration:

# Display IPv6 PIM information on Router D.

[RouterD] display pim ipv6 interface

Interface NbrCnt HelloInt DR-Pri DR-Address

GE3/1/1 0 30 1 4001::1

(local)

Ser4/1/9/1:0 0 30 1 1002::2

(local)

Pos5/1/1 1 30 1 2002::2

(local)

Pos5/1/2 1 30 1 3001::2

(local)

# Display IPv6 PIM neighboring relationships on Router D.

[RouterD] display pim ipv6 neighbor

Total Number of Neighbors = 3

Neighbor Interface Uptime Expires Dr-Priority

1002::1 Ser4/1/9/1:0 00:04:00 00:01:29 1

2002::1 Pos5/1/1 00:04:16 00:01:29 3

3001::1 Pos5/1/2 00:03:54 00:01:17 5

Assume that Host A needs to receive information addressed to an IPv6 multicast group G (FF0E::101). Once the IPv6 multicast source S (4001::100/64) sends IPv6 multicast packets to the IPv6 multicast group G, an SPT is established through traffic flooding. Routers on the SPT path (Router A and Router D) have their (S, G) entries. Host A sends a request of joining the multicast group G to Router A, and a (*, G) entry is generated on Router A. To view the IPv6 PIM routing information on a router, use the display pim ipv6 routing-table command. For example:

# Display IPv6 PIM multicast routing table information on Router A.

[RouterA] display pim ipv6 routing-table

Total 1 (*, G) entry; 1 (S, G) entry

(*, FF0E::101)

Protocol: pim-dm, Flag: WC

UpTime: 00:01:24

Upstream interface: NULL

Upstream neighbor: NULL

RPF prime neighbor: NULL

Downstream interface(s) information:

Total number of downstreams: 1

1: GigabitEthernet3/1/1

Protocol: mld, UpTime: 00:01:20, Expires: never

(4001::100, FF0E::101)

Protocol: pim-dm, Flag: ACT

UpTime: 00:01:20

Upstream interface: Serial4/1/9/1:0

Upstream neighbor: 1002::2

RPF prime neighbor: 1002::2

Downstream interface(s) information:

Total number of downstreams: 1

1: GigabitEthernet3/1/1

Protocol: pim-dm, UpTime: 00:01:20, Expires: never

# Display IPv6 PIM multicast routing table information on Router D.

[RouterD] display pim ipv6 routing-table

Total 0 (*, G) entry; 1 (S, G) entry

(4001::100, FF0E::101)

Protocol: pim-dm, Flag: LOC ACT

UpTime: 00:02:19

Upstream interface: GigabitEthernet3/1/1

Upstream neighbor: NULL

RPF prime neighbor: NULL

Downstream interface(s) information:

Total number of downstreams: 3

1: Serial4/1/9/1:0

Protocol: pim-dm, UpTime: 00:02:19, Expires: never

2: Pos5/1/1

Protocol: pim-dm, UpTime: 00:02:19, Expires: never

3: Pos5/1/2

Protocol: pim-dm, UpTime: 00:02:19, Expires: never

IPv6 PIM-SM non-scoped zone configuration example

Network requirements

Receivers receive VOD information through multicast. The receiver groups of different organizations form stub networks, and one or more receiver hosts exist in each stub network. The entire IPv6 PIM domain operates in the sparse mode.

Host A and Host C are IPv6 multicast receivers in two stub networks, N1 and N2.

Both POS 5/1/1 on Router D and POS 5/1/3 on Router E act as C-BSRs and C-RPs; the C-BSR on Router E has a higher priority; the range of multicast groups served by the C-RP is FF0E::101/64; modify the hash mask length to map a certain number of consecutive group addresses within the range to the two C-RPs.

MLDv1 runs between Router A and N1 and between Router B/Router C and N2.

Figure 15 Network diagram

Device	Interface	IP address	Device	Interface	IP address
Router A	GE3/1/1	1001::1/64	Router D	GE3/1/1	4001::1/64
	S4/1/9/1:0	1002::1/64		S4/1/9/1:0	1002::2/64
	POS5/1/1	1003::1/64		POS5/1/1	4002::1/64
Router B	GE3/1/1	2001::1/64	Router E	POS5/1/1	3001::2/64
	POS5/1/1	2002::1/64		POS5/1/2	2002::2/64
Router C	GE3/1/1	2001::2/64		POS5/1/3	1003::2/64
	POS5/1/1	3001::1/64		POS5/1/4	4002::2/64

Configuration procedure

1. Enable IPv6 forwarding, assign IPv6 addresses, and configure IPv6 unicast routing:

Enable IPv6 forwarding and assign the IP address and prefix length for each interface as per Figure 15. (Details not shown)

Configure the OSPFv3 protocol for interoperation among the routers in the IPv6 PIM-SM domain. Ensure the network-layer interoperation in the IPv6 PIM-SM domain and enable dynamic update of routing information among the routers through an IPv6 unicast routing protocol. (Details not shown)

2. Enable IPv6 multicast routing, IPv6 PIM-SM and MLD:

# Enable IPv6 multicast routing on Router A, enable IPv6 PIM-SM on each interface, and enable MLD on GigabitEthernet 3/1/1, which connects Router A to N1.

<RouterA> system-view

[RouterA] multicast ipv6 routing-enable

[RouterA] interface GigabitEthernet3/1/1

[RouterA-GigabitEthernet3/1/1] mld enable

[RouterA-GigabitEthernet3/1/1] pim ipv6 sm

[RouterA-GigabitEthernet3/1/1] quit

[RouterA] interface Serial 4/1/9/1:0

[RouterA-Serial4/1/9/1:0] pim ipv6 sm

[RouterA-Serial4/1/9/1:0] quit

[RouterA] interface pos 5/1/1

[RouterA-Pos5/1/1] pim ipv6 sm

[RouterA-Pos5/1/1] quit

The configuration on Router B and Router C is similar to that on Router A. The configuration on Router D and Router E is also similar to that on Router A except that it is not necessary to enable MLD on the corresponding interfaces on these two routers.

3. Configure C-BSRs and C-RPs:

# On Router D, configure the service scope of RP advertisements, specify a C-BSR and a C-RP, and set the hash mask length to 128 and the priority of the C-BSR to 10.

<RouterD> system-view

[RouterD] acl ipv6 number 2005

[RouterD-acl6-basic-2005] rule permit source ff0e::101 64

[RouterD-acl6-basic-2005] quit

[RouterD] pim ipv6

[RouterD-pim6] c-bsr 4002::1 128 10

[RouterD-pim6] c-rp 4002::1 group-policy 2005

[RouterD-pim6] quit

# On Router E, configure the service scope of RP advertisements, specify a C-BSR and a C-RP, and set the hash mask length to 128 and the priority of the C-BSR to 20.

<RouterE> system-view

[RouterE] acl ipv6 number 2005

[RouterE-acl6-basic-2005] rule permit source ff0e::101 64

[RouterE-acl6-basic-2005] quit

[RouterE] pim ipv6

[RouterE-pim6] c-bsr 1003::2 128 20

[RouterE-pim6] c-rp 1003::2 group-policy 2005

[RouterE-pim6] quit

4. Verify the configuration:

# Display IPv6 PIM configuration information on Router A.

[RouterA] display pim ipv6 interface

Interface NbrCnt HelloInt DR-Pri DR-Address

GE3/1/1 0 30 1 1001::1

(local)

Ser4/1/9/1:0 1 30 1 1002::2

Pos5/5/1 1 30 1 1003::2

# Display BSR information and the locally configured C-RP information in effect on Router A.

[RouterA] display pim ipv6 bsr-info

Elected BSR Address: 1003::2

Priority: 20

Hash mask length: 128

State: Accept Preferred

Uptime: 00:04:22

Expires: 00:01:46

# Display BSR information on Router D and the locally configured C-RP information in effect.

[RouterD] display pim ipv6 bsr-info

Elected BSR Address: 1003::2

Priority: 20

Hash mask length: 128

State: Elected

Uptime: 00:05:26

Expires: 00:01:45

Candidate BSR Address: 4002::1

Priority: 10

Hash mask length: 128

State: Candidate

Candidate RP: 4002::1(Pos5/1/1)

Priority: 192

HoldTime: 130

Advertisement Interval: 60

Next advertisement scheduled at: 00:00:48

# Display BSR information on Router E and the locally configured C-RP information in effect.

[RouterE] display pim ipv6 bsr-info

Elected BSR Address: 1003::2

Priority: 20

Hash mask length: 128

State: Elected

Uptime: 00:01:10

Next BSR message scheduled at: 00:01:48

Candidate BSR Address: 1003::2

Priority: 20

Hash mask length: 128

State: Elected

Candidate RP: 1003::2(Pos5/1/3)

Priority: 192

HoldTime: 130

Advertisement Interval: 60

Next advertisement scheduled at: 00:00:48

# Display RP information on Router A.

[RouterA] display pim ipv6 rp-info

PIM-SM BSR RP information:

prefix/prefix length: FF0E::101/64

RP: 4002::1

Priority: 192

HoldTime: 130

Uptime: 00:05:19

Expires: 00:02:11

RP: 1003::2

Priority: 192

HoldTime: 130

Uptime: 00:05:19

Expires: 00:02:11

Assume that Host A needs to receive information addressed to an IPv6 multicast group G (FF0E::100). The RP for multicast group G is Router E as a result of hash calculation, so an RPT will be built between Router A and Router E. When the multicast source S (4001::100/64) registers with the RP, an SPT will be built between Router D and Router E. Upon receiving IPv6 multicast data, Router A immediately switches from the RPT to the SPT. Routers on the RPT path (Router A and Router E) have a (*, G) entry, while routers on the SPT path (Router A and Router D) have an (S, G) entry. You can use the display pim ipv6 routing-table command to view the PIM routing table information on the routers. For example:

# Display IPv6 PIM multicast routing table information on Router A.

[RouterA] display pim ipv6 routing-table

Total 1 (*, G) entry; 1 (S, G) entry

(*, FF0E::100)

RP: 1003::2

Protocol: pim-sm, Flag: WC

UpTime: 00:03:45

Upstream interface: Pos5/1/1

Upstream neighbor: 1003::2

RPF prime neighbor: 1003::2

Downstream interface(s) information:

Total number of downstreams: 1

1: GigabitEthernet3/1/1

Protocol: mld, UpTime: 00:02:15, Expires: 00:03:06

(4001::100, FF0E::100)

RP: 1003::2

Protocol: pim-sm, Flag: SPT ACT

UpTime: 00:02:15

Upstream interface: Serial4/1/9/1:0

Upstream neighbor: 1002::2

RPF prime neighbor: 1002::2

Downstream interface(s) information:

Total number of downstreams: 1

1: GigabitEthernet3/1/1

Protocol: pim-sm, UpTime: 00:02:15, Expires: 00:03:06

# Display IPv6 PIM multicast routing table information on Router D.

[RouterD] display pim ipv6 routing-table

Total 0 (*, G) entry; 1 (S, G) entry

(4001::100, FF0E::100)

RP: 1003::2

Protocol: pim-sm, Flag: SPT LOC ACT

UpTime: 00:14:44

Upstream interface: GigabitEthernet3/1/1

Upstream neighbor: NULL

RPF prime neighbor: NULL

Downstream interface(s) information:

Total number of downstreams: 1

1: Pos5/1/1

Protocol: mld, UpTime: 00:14:44, Expires: 00:02:26

# Display IPv6 PIM routing table information on Router E.

[RouterE] display pim ipv6 routing-table

Total 1 (*, G) entry; 0 (S, G) entry

(*, FF0E::100)

RP: 1003::2 (local)

Protocol: pim-sm, Flag: WC

UpTime: 00:16:56

Upstream interface: Register

Upstream neighbor: 4002::1

RPF prime neighbor: 4002::1

Downstream interface(s) information:

Total number of downstreams: 1

1: Pos5/1/3

Protocol: pim-sm, UpTime: 00:16:56, Expires: 00:02:34

IPv6 PIM-SM admin-scope zone configuration example

Network requirements

Receivers receive VOD information through multicast. The entire IPv6 PIM-SM domain is divided into IPv6 admin-scope zone 1, IPv6 admin-scope zone 2, and the IPv6 global scope zone. Router B, Router C, and Router D are ZBRs of the three domains respectively.

Source 1 and Source 2 send different multicast information to FF14::101. Host A receives the multicast information from Source 1 only, while Host B receives the multicast information from Source 2 only. Source 3 sends multicast information to FF1E::202. Host C is a multicast receiver for this multicast group.

Serial4/1/9/1:0 of Router B acts as a C-BSR and C-RP of IPv6 admin-scope zone 1, which serve the IPv6 multicast groups with the Scope field value in their group addresses being 4. Serial4/1/9/1:0 of Router D acts as a C-BSR and C-RP of admin-scope zone 2, which also serve the IPv6 multicast groups with the Scope field value in their group addresses being 4. Serial4/1/9/1:0 of Router F acts as a C-BSR and a C-RP of the global scope zone, which serve IPv6 multicast groups with the Scope field value in their group addresses being 14.

MLDv1 runs between Router A, Router E, Router I, and their respective receivers.

Figure 16 Network diagram

Device	Interface	IP address	Device	Interface	IP address
Router A	GE3/1/1	1001::1/64	Router D	S4/1/9/1:0	3002::2/64
	S4/1/9/1:0	1002::1/64		S4/1/9/1:1	6001::1/64
Router B	GE3/1/1	2001::1/64		POS5/1/1	6002::1/64
	S4/1/9/1:0	1002::2/64	Router E	GE3/1/1	7001::1/64
	POS5/1/1	2002::1/64		S4/1/9/1:0	3003::2/64
	POS5/1/2	2003::1/64		S4/1/9/1:1	6001::2/64
Router C	GE3/1/1	3001::1/64	Router F	S4/1/9/1:0	8001::1/64
	S4/1/9/1:0	3002::1/64		POS5/1/1	6002::2/64
	S4/1/9/1:1	3003::1/64		POS5/1/2	2003::2/64
	POS5/1/1	2002::2/64	Router G	GE3/1/1	9001::1/64
	POS5/1/2	3004::1/64		S4/1/9/1:0	8001::2/64
Router H	S4/1/9/1:0	4001::1/64	Source 1	—	2001::100/64
	POS5/1/1	3004::2/64	Source 2	—	3001::100/64
Router I	GE3/1/1	5001::1/64	Source 3	—	9001::100/64
	S4/1/9/1:0	4001::2/64

Configuration procedure

1. Assign IPv6 addresses and configure unicast routing:

Assign the IPv6 address and prefix length for each interface as per Figure 16. (Details not shown)

Configure OSPFv3 on the routers in the IPv6 PIM-SM domain to ensure network-layer reachability among them. (Details not shown)

2. Enable IPv6 multicast routing and IPv6 administrative scoping, and enable IPv6 PIM-SM and MLD:

# Enable IPv6 multicast routing and IPv6 administrative scoping on Router A, enable IPv6 PIM-SM on each interface, and enable MLD on the host-side interface GE3/1/1.

<RouterA> system-view

[RouterA] multicast ipv6 routing-enable

[RouterA] pim ipv6

[RouterA-pim6] c-bsr admin-scope

[RouterA-pim6] quit

[RouterA] interface GigabitEthernet 3/1/1

[RouterA-GigabitEthernet3/1/1] mld enable

[RouterA-GigabitEthernet3/1/1] pim ipv6 sm

[RouterA-GigabitEthernet3/1/1] quit

[RouterA] interface serial 4/1/9/1:0

[RouterA-Serial4/1/9/1:0] pim ipv6 sm

[RouterA-Serial4/1/9/1:0] quit

The configuration on Router E and Router I is similar to the configuration on Router A.

# On Router B, enable IPv6 multicast routing and IPv6 administrative scoping, and enable IPv6 PIM-SM on each interface.

<RouterB> system-view

[RouterB] multicast ipv6 routing-enable

[RouterB] pim ipv6

[RouterB-pim6] c-bsr admin-scope

[RouterB-pim6] quit

[RouterB] interface GigabitEthernet 3/1/1

[RouterB-GigabitEthernet3/1/1] pim ipv6 sm

[RouterB-GigabitEthernet3/1/1] quit

[RouterB] interface serial 4/1/9/1:0

[RouterB-Serial4/1/9/1:0] pim ipv6 sm

[RouterB-Serial4/1/9/1:0] quit

[RouterB] interface pos 5/1/1

[RouterB-Pos5/1/1] pim ipv6 sm

[RouterB-Pos5/1/1] quit

[RouterB] interface pos 5/1/2

[RouterB-Pos5/1/2] pim ipv6 sm

[RouterB-Pos5/1/2] quit

The configuration on Router C, Router D, Router F, Router G, and Router H is similar to the configuration on Router B. (Details not shown)

3. Configure an IPv6 admin-scope zone boundary:

# On Router B, configure POS 5/1/1 and POS 5/1/2 as the boundary of IPv6 admin-scope zone 1.

[RouterB] interface pos 5/1/1

[RouterB-Pos5/1/1] multicast ipv6 boundary scope 4

[RouterB-Pos5/1/1] quit

[RouterB] interface pos 5/1/2

[RouterB-Pos5/1/2] multicast ipv6 boundary scope 4

[RouterB-Pos5/1/2] quit

# On Router C, configure POS 5/1/1 and POS 5/1/2 as the boundary of IPv6 admin-scope zone 2.

<RouterC> system-view

[RouterC] interface pos 5/1/1

[RouterC-Pos5/1/1] multicast ipv6 boundary scope 4

[RouterC-Pos5/1/1] quit

[RouterC] interface pos 5/1/2

[RouterC-Pos5/1/2] multicast ipv6 boundary scope 4

[RouterC-Pos5/1/2] quit

# On Router D, configure POS 5/1/1 as the boundary of admin-scope zone 2.

<RouterD> system-view

[RouterD] interface pos 5/1/1

[RouterD-Pos5/1/1] multicast ipv6 boundary scope 4

[RouterD-Pos5/1/1] quit

4. Configure C-BSRs and C-RPs:

# On Router B, configure the service scope of RP advertisements and configure Serial 4/1/9/1:0 as a C-BSR and C-RP of admin-scope zone 1.

[RouterB] pim ipv6

[RouterB-pim6] c-bsr scope 4

[RouterB-pim6] c-bsr 1002::2

[RouterB-pim6] c-rp 1002::2 scope 4

[RouterB-pim6] quit

# On Router D, configure the service scope of RP advertisements and configure Serial 4/1/9/1:0 as a C-BSR and C-RP of admin-scope zone 2.

[RouterD] pim ipv6

[RouterD-pim6] c-bsr scope 4

[RouterD-pim6] c-bsr 3002::2

[RouterD-pim6] c-rp 3002::2 scope 4

[RouterD-pim6] quit

# On Router F, configure Serial 4/1/9/1:0 as a C-BSR and C-RP in the global scope zone.

<RouterF> system-view

[RouterF] pim ipv6

[RouterF-pim6] c-bsr scope global

[RouterF-pim6] c-bsr 8001::1

[RouterF-pim6] c-rp 8001::1

[RouterF-pim6] quit

5. Verify the configuration:

# Display BSR information and the locally configured C-RP information on Router B.

[RouterB] display pim ipv6 bsr-info

Elected BSR Address: 8001::1

Priority: 64

Hash mask length: 126

State: Accept Preferred

Scope: 14

Uptime: 00:01:45

Expires: 00:01:25

Elected BSR Address: 1002::2

Priority: 64

Hash mask length: 126

State: Elected

Scope: 4

Uptime: 00:04:54

Next BSR message scheduled at: 00:00:06

Candidate BSR Address: 1002::2

Priority: 64

Hash mask length: 126

State: Elected

Scope: 4

Candidate RP: 1002::2(Serial4/1/9/1:0)

Priority: 192

HoldTime: 130

Advertisement Interval: 60

Next advertisement scheduled at: 00:00:15

# Display BSR information and the locally configured C-RP information on Router D.

[RouterD] display pim ipv6 bsr-info

Elected BSR Address: 8001::1

Priority: 64

Hash mask length: 126

State: Accept Preferred

Scope: 14

Uptime: 00:01:45

Expires: 00:01:25

Elected BSR Address: 3002::2

Priority: 64

Hash mask length: 126

State: Elected

Scope: 4

Uptime: 00:03:48

Next BSR message scheduled at: 00:01:12

Candidate BSR Address: 3002::2

Priority: 64

Hash mask length: 126

State: Elected

Scope: 4

Candidate RP: 3002::2(Serial4/1/9/1:0)

Priority: 192

HoldTime: 130

Advertisement Interval: 60

Next advertisement scheduled at: 00:00:10

# Display BSR information and the locally configured C-RP information on Router F.

[RouterF] display pim ipv6 bsr-info

Elected BSR Address: 8001::1

Priority: 64

Hash mask length: 126

State: Elected

Scope: 14

Uptime: 00:01:11

Next BSR message scheduled at: 00:00:49

Candidate BSR Address: 8001::1

Priority: 64

Hash mask length: 126

State: Elected

Scope: 14

Candidate RP: 8001::1(Serial4/1/9/1:0)

Priority: 192

HoldTime: 130

Advertisement Interval: 60

Next advertisement scheduled at: 00:00:55

# Display RP information on Router B.

[RouterB] display pim ipv6 rp-info

PIM-SM BSR RP information:

prefix/prefix length: FF0E::/16

RP: 8001::1

Priority: 192

HoldTime: 130

Uptime: 00:03:39

Expires: 00:01:51

prefix/prefix length: FF1E::/16

RP: 8001::1

Priority: 192

HoldTime: 130

Uptime: 00:03:39

Expires: 00:01:51

prefix/prefix length: FF2E::/16

RP: 8001::1

Priority: 192

HoldTime: 130

Uptime: 00:03:39

Expires: 00:01:51

prefix/prefix length: FF3E::/16

RP: 8001::1

Priority: 192

HoldTime: 130

Uptime: 00:03:39

Expires: 00:01:51

prefix/prefix length: FF4E::/16

RP: 8001::1

Priority: 192

HoldTime: 130

Uptime: 00:03:39

Expires: 00:01:51

prefix/prefix length: FF5E::/16

RP: 8001::1

Priority: 192

HoldTime: 130

Uptime: 00:03:39

Expires: 00:01:51

prefix/prefix length: FF6E::/16

RP: 8001::1

Priority: 192

HoldTime: 130

Uptime: 00:03:39

Expires: 00:01:51

prefix/prefix length: FF7E::/16

RP: 8001::1

Priority: 192

HoldTime: 130

Uptime: 00:03:39

Expires: 00:01:51

prefix/prefix length: FF8E::/16

RP: 8001::1

Priority: 192

HoldTime: 130

Uptime: 00:03:39

Expires: 00:01:51

prefix/prefix length: FF9E::/16

RP: 8001::1

Priority: 192

HoldTime: 130

Uptime: 00:03:39

Expires: 00:01:51

prefix/prefix length: FFAE::/16

RP: 8001::1

Priority: 192

HoldTime: 130

Uptime: 00:03:39

Expires: 00:01:51

prefix/prefix length: FFBE::/16

RP: 8001::1

Priority: 192

HoldTime: 130

Uptime: 00:03:39

Expires: 00:01:51

prefix/prefix length: FFCE::/16

RP: 8001::1

Priority: 192

HoldTime: 130

Uptime: 00:03:39

Expires: 00:01:51

prefix/prefix length: FFDE::/16

RP: 8001::1

Priority: 192

HoldTime: 130

Uptime: 00:03:39

Expires: 00:01:51

prefix/prefix length: FFEE::/16

RP: 8001::1

Priority: 192

HoldTime: 130

Uptime: 00:03:39

Expires: 00:01:51

prefix/prefix length: FFFE::/16

RP: 8001::1

Priority: 192

HoldTime: 130

Uptime: 00:03:39

Expires: 00:01:51

prefix/prefix length: FF04::/16

RP: 1002::2

Priority: 192

HoldTime: 130

Uptime: 00:03:39

Expires: 00:01:51

prefix/prefix length: FF14::/16

RP: 1002::2

Priority: 192

HoldTime: 130

Uptime: 00:03:39

Expires: 00:01:51

prefix/prefix length: FF24::/16

RP: 1002::2

Priority: 192

HoldTime: 130

Uptime: 00:03:39

Expires: 00:01:51

prefix/prefix length: FF34::/16

RP: 1002::2

Priority: 192

HoldTime: 130

Uptime: 00:03:39

Expires: 00:01:51

prefix/prefix length: FF44::/16

RP: 1002::2

Priority: 192

HoldTime: 130

Uptime: 00:03:39

Expires: 00:01:51

prefix/prefix length: FF54::/16

RP: 1002::2

Priority: 192

HoldTime: 130

Uptime: 00:03:39

Expires: 00:01:51

prefix/prefix length: FF64::/16

RP: 1002::2

Priority: 192

HoldTime: 130

Uptime: 00:03:39

Expires: 00:01:51

prefix/prefix length: FF74::/16

RP: 1002::2

Priority: 192

HoldTime: 130

Uptime: 00:03:39

Expires: 00:01:51

prefix/prefix length: FF84::/16

RP: 1002::2

Priority: 192

HoldTime: 130

Uptime: 00:03:39

Expires: 00:01:51

prefix/prefix length: FF94::/16

RP: 1002::2

Priority: 192

HoldTime: 130

Uptime: 00:03:39

Expires: 00:01:51

prefix/prefix length: FFA4::/16

RP: 1002::2

Priority: 192

HoldTime: 130

Uptime: 00:03:39

Expires: 00:01:51

prefix/prefix length: FFB4::/16

RP: 1002::2

Priority: 192

HoldTime: 130

Uptime: 00:03:39

Expires: 00:01:51

prefix/prefix length: FFC4::/16

RP: 1002::2

Priority: 192

HoldTime: 130

Uptime: 00:03:39

Expires: 00:01:51

prefix/prefix length: FFD4::/16

RP: 1002::2

Priority: 192

HoldTime: 130

Uptime: 00:03:39

Expires: 00:01:51

prefix/prefix length: FFE4::/16

RP: 1002::2

Priority: 192

HoldTime: 130

Uptime: 00:03:39

Expires: 00:01:51

prefix/prefix length: FFF4::/16

RP: 1002::2

Priority: 192

HoldTime: 130

Uptime: 00:03:39

Expires: 00:01:51

# View the RP information on Router F.

[RouterF] display pim rp-info

PIM-SM BSR RP information:

prefix/prefix length: FF0E::/16

RP: 8001::1

Priority: 192

HoldTime: 130

Uptime: 00:03:39

Expires: 00:01:51

prefix/prefix length: FF1E::/16

RP: 8001::1

Priority: 192

HoldTime: 130

Uptime: 00:03:39

Expires: 00:01:51

prefix/prefix length: FF2E::/16

RP: 8001::1

Priority: 192

HoldTime: 130

Uptime: 00:03:39

Expires: 00:01:51

prefix/prefix length: FF3E::/16

RP: 8001::1

Priority: 192

HoldTime: 130

Uptime: 00:03:39

Expires: 00:01:51

prefix/prefix length: FF4E::/16

RP: 8001::1

Priority: 192

HoldTime: 130

Uptime: 00:03:39

Expires: 00:01:51

prefix/prefix length: FF5E::/16

RP: 8001::1

Priority: 192

HoldTime: 130

Uptime: 00:03:39

Expires: 00:01:51

prefix/prefix length: FF6E::/16

RP: 8001::1

Priority: 192

HoldTime: 130

Uptime: 00:03:39

Expires: 00:01:51

prefix/prefix length: FF7E::/16

RP: 8001::1

Priority: 192

HoldTime: 130

Uptime: 00:03:39

Expires: 00:01:51

prefix/prefix length: FF8E::/16

RP: 8001::1

Priority: 192

HoldTime: 130

Uptime: 00:03:39

Expires: 00:01:51

prefix/prefix length: FF9E::/16

RP: 8001::1

Priority: 192

HoldTime: 130

Uptime: 00:03:39

Expires: 00:01:51

prefix/prefix length: FFAE::/16

RP: 8001::1

Priority: 192

HoldTime: 130

Uptime: 00:03:39

Expires: 00:01:51

prefix/prefix length: FFBE::/16

RP: 8001::1

Priority: 192

HoldTime: 130

Uptime: 00:03:39

Expires: 00:01:51

prefix/prefix length: FFCE::/16

RP: 8001::1

Priority: 192

HoldTime: 130

Uptime: 00:03:39

Expires: 00:01:51

prefix/prefix length: FFDE::/16

RP: 8001::1

Priority: 192

HoldTime: 130

Uptime: 00:03:39

Expires: 00:01:51

prefix/prefix length: FFEE::/16

RP: 8001::1

Priority: 192

HoldTime: 130

Uptime: 00:03:39

Expires: 00:01:51

prefix/prefix length: FFFE::/16

RP: 8001::1

Priority: 192

HoldTime: 130

Uptime: 00:03:39

Expires: 00:01:51

IPv6 BIDIR-PIM configuration example

Network requirements

In the IPv6 BIDIR-PIM domain shown in Figure 17, Source 1 and Source 2 send different IPv6 multicast information to IPv6 multicast group FF14::101. Host A and Host B receive IPv6 multicast information from the two sources.

Serial2/1/9/1:0 of Router C acts as a C-BSR, and loopback interface 0 acts as a C-RP of the IPv6 BIDIR-PIM domain.

MLDv1 runs between Router B and Host A and between Router D and Host B.

Figure 17 Network diagram

Device	Interface	IPv6 address	Device	Interface	IPv6 address
Router A	GE3/1/1	1001::1/64	Router D	GE3/1/1	4001::1/64
	S2/1/9/1:0	1002::1/64		GE3/1/2	5001::1/64
Router B	GE3/1/1	2001::1/64		S2/1/9/1:0	3001::2/64
	S2/1/9/1:0	1002::2/64	Source 1	-	1001::2/64
	S2/1/9/2:0	2002::1/64	Source 2	-	5001::2/64
Router C	S2/1/9/1:0	2002::2/64	Receiver 1	-	2001::2/64
	S2/1/9/2:0	3001::1/64	Receiver 2	-	4001::2/64
	Loop0	6001::1/128

Configuration procedure

1. Enable IPv6 forwarding, assign IPv6 addresses, and configure IPv6 unicast routing:

Enable IPv6 forwarding on each router, and assign the IPv6 address and prefix length for each interface as per Figure 17. (Details not shown)

Configure OSPFv3 on the routers in the IPv6 BIDIR-PIM domain to ensure network-layer reachability among them. (Details not shown)

2. Enable IPv6 multicast routing, IPv6 PIM-SM, IPv6 BIDIR-PIM, and MLD:

# On Router A, enable IPv6 multicast routing, enable IPv6 PIM-SM on each interface, and enable IPv6 BIDIR-PIM.

<RouterA> system-view

[RouterA] multicast ipv6 routing-enable

[RouterA] interface GigabitEthernet 3/1/1

[RouterA-GigabitEthernet3/1/1] pim ipv6 sm

[RouterA-GigabitEthernet3/1/1] quit

[RouterA] interface Serial 2/1/9/1:0

[RouterA-Serial2/1/9/1:0] pim ipv6 sm

[RouterA-Serial2/1/9/1:0] quit

[RouterA] pim ipv6

[RouterA-pim6] bidir-pim enable

[RouterA-pim6] quit

# On Router B, enable IPv6 multicast routing, enable IPv6 PIM-SM on each interface, enable MLD on interface GigabitEthernet 3/1/1, and enable IPv6 BIDIR-PIM.

<RouterB> system-view

[RouterB] multicast ipv6routing-enable

[RouterB] interface GigabitEthernet 3/1/1

[RouterB-GigabitEthernet3/1/1] mld enable

[RouterB-GigabitEthernet3/1/1] pim ipv6 sm

[RouterB-GigabitEthernet3/1/1] quit

[RouterB] interface Serial 2/1/9/1:0

[RouterB-Serial2/1/9/1:0] pim ipv6 sm

[RouterB-Serial2/1/9/1:0] quit

[RouterB] interface Serial 2/1/9/2:0

[RouterB-Serial2/1/9/2:0] pim ipv6 sm

[RouterB-Serial2/1/9/2:0] quit

[RouterB] pim ipv6

[RouterB-pim6] bidir-pim enable

[RouterB-pim6] quit

# On Router C, enable IPv6 multicast routing, enable IPv6 PIM-SM on each interface, and enable IPv6 BIDIR-PIM.

<RouterC> system-view

[RouterC] multicast ipv6 routing-enable

[RouterC] interface Serial 2/1/9/1:0

[RouterC-Serial2/1/9/1:0] pim ipv6 sm

[RouterC-Serial2/1/9/1:0] quit

[RouterC] interface Serial 2/1/9/2:0

[RouterC-Serial2/1/9/2:0] pim ipv6 sm

[RouterC-Serial2/1/9/2:0] quit

[RouterC] interface loopback 0

[RouterC-LoopBack0] pim ipv6 sm

[RouterC-LoopBack0] quit

[RouterC] pim ipv6

[RouterC-pim6] bidir-pim enable

# On Router D, enable IPv6 multicast routing, enable IPv6 PIM-SM on each interface, enable MLD on interface GigabitEthernet 3/1/1, and enable IPv6 BIDIR-PIM.

<RouterD> system-view

[RouterD] multicast ipv6 routing-enable

[RouterD] interface GigabitEthernet 3/1/1

[RouterD-GigabitEthernet3/1/1] mld enable

[RouterD-GigabitEthernet3/1/1] pim ipv6 sm

[RouterD-GigabitEthernet3/1/1] quit

[RouterD] interface GigabitEthernet 3/1/2

[RouterD-GigabitEthernet3/1/2] pim ipv6 sm

[RouterD-GigabitEthernet3/1/2] quit

[RouterD] interface Serial 2/1/9/1:0

[RouterD-Serial2/1/9/1:0] pim ipv6 sm

[RouterD-Serial2/1/9/1:0] quit

[RouterD] pim ipv6

[RouterD-pim6] bidir-pim enable

[RouterD-pim6] quit

3. Configure C-BSR and C-RP:

# On Router C, configure Serial2/1/9/1:0 as a C-BSR, and loopback interface 0 as a C-RP for the entire IPv6 BIDIR-PIM domain.

[RouterC-pim6] c-bsr 3001::2

[RouterC-pim6] c-rp 6001::1 bidir

[RouterC-pim6] quit

4. Verify the configuration:

# Display the DF information of IPv6 BIDIR-PIM on Router A.

[RouterA] display pim ipv6 df-info

RP Address: 6001::1

GE3/1/1 Win 100 2 01:08:50 FE80::200:5EFF:

FE71:2800 (local)

Ser2/1/9/1:0 Lose 100 1 01:07:49 FE80::20F:E2FF:

FE38:4E01

# Display the DF information of IPv6 BIDIR-PIM on Router B.

[RouterB] display pim ipv6 df-info

RP Address: 6001::1

Interface State DF-Pref DF-Metric DF-Uptime DF-Address

GE3/1/1 Win 100 1 01:24:09 FE80::200:5EFF:

FE71:2801 (local)

Ser2/1/9/1:0 Win 100 1 01:24:09 FE80::20F:E2FF:

FE38:4E01 (local)

Ser2/1/9/2:0 Lose 0 0 01:23:12 FE80::20F:E2FF:

FE15:5601

# Display the DF information of IPv6 BIDIR-PIM on Router C.

[RouterC] display pim ipv6 df-info

RP Address: 6001::1

Interface State DF-Pref DF-Metric DF-Uptime DF-Address

Loop0 - - - - -

Ser2/1/9/1:0 Win 0 0 01:06:07 FE80::20F:E2FF:

FE15:5601 (local)

Ser2/1/9/2:0 Win 0 0 01:06:07 FE80::20F:E2FF:

FE15:5602 (local)

# Display the DF information of IPv6 BIDIR-PIM on Router D.

[RouterD] display pim ipv6 df-info

RP Address: 6001::1

Interface State DF-Pref DF-Metric DF-Uptime DF-Address

GE3/1/1 Win 100 1 01:19:53 FE80::200:5EFF:

FE71:2803 (local)

GE3/1/2 Win 100 1 00:39:34 FE80::200:5EFF:

FE71:2802 (local)

Ser2/1/9/2:0 Lose 0 0 01:21:40 FE80::20F:E2FF:

FE15:5602

To view the DF information of the IPv6 multicast forwarding table on a router, use the display multicast ipv6 forwarding-table df-info command. For more information about this command, see IP Multicast Command Reference.

# Display the DF information of the IPv6 multicast forwarding table on Router A.

[RouterA] display multicast ipv6 forwarding-table df-info

Multicast DF information

Total 1 RP

Total 1 RP matched

00001. RP Address: 6001::1

MID: 0, Flags: 0x2100000:0

Uptime: 00:08:32

RPF interface: Serial2/1/9/1:0

List of 1 DF interfaces:

1: GigabitEthernet3/1/1

# Display the DF information of the IPv6 multicast forwarding table on Router B.

[RouterB] display multicast ipv6 forwarding-table df-info

Multicast DF information

Total 1 RP

Total 1 RP matched

00001. RP Address: 6001::1

MID: 0, Flags: 0x2100000:0

Uptime: 00:06:24

RPF interface: Serial2/1/9/2:0

List of 2 DF interfaces:

1: GigabitEthernet3/1/1

2: Serial2/1/9/1:0

# Display the DF information of the IPv6 multicast forwarding table on Router C.

[RouterC] display multicast ipv6 forwarding-table df-info

Multicast DF information

Total 1 RP

Total 1 RP matched

00001. RP Address: 6001::1

MID: 0, Flags: 0x2100000:0

Uptime: 00:07:21

RPF interface: LoopBack0

List of 2 DF interfaces:

1: Serial2/1/9/1:0

2: Serial2/1/9/2:0

# Display the DF information of the IPv6 multicast forwarding table on Router D.

[RouterD] display multicast ipv6 forwarding-table df-info

Multicast DF information

Total 1 RP

Total 1 RP matched

00001. RP Address: 6001::1

MID: 0, Flags: 0x2100000:0

Uptime: 00:05:12

RPF interface: Serial2/1/9/1:0

List of 2 DF interfaces:

1: GigabitEthernet3/1/1

2: GigabitEthernet3/1/2

# Display IPv6 PIM multicast routing table information on Router A.

[RouterA]display pim ipv6 routing-table

Total 1 (*, G) entries; 0 (S, G) entry

(*, FF1E::1)

RP: 3::3 (local)

Protocol: pim-sm, Flag: WC BIDIR ACT

UpTime: 00:01:01

Upstream interface: LoopBack0

Upstream neighbor: NULL

RPF prime neighbor: NULL

Downstream interface(s) information:

Total number of downstreams: 2

1: LoopBack0

Protocol: pim-sm, UpTime: - , Expires: -

2: GigabitEthernet3/1/5

Protocol: pim-sm, UpTime: 00:00:34, Expires: 00:02:56

IPv6 PIM-SSM configuration example

Network requirements

Host A and Host C are IPv6 multicast receivers in two stub networks, N1 and N2.

Router E connects to Router A, Router B, Router C and Router D.

The SSM group range is FF3E::/64.

MLDv2 runs between Router A and N1 and between Router B/Router C and N2.

Figure 18 Network diagram

Device	Interface	IP address	Device	Interface	IP address
Router A	GE3/1/1	1001::1/64	Router D	GE3/1/1	4001::1/64
	S4/1/9/1:0	1002::1/64		S4/1/9/1:0	1002::2/64
	POS5/1/1	1003::1/64		POS5/1/1	4002::1/64
Router B	GE3/1/1	2001::1/64	Router E	POS5/1/1	3001::2/64
	POS5/1/1	2002::1/64		POS5/1/2	2002::2/64
Router C	GE3/1/1	2001::2/64		POS5/1/3	1003::2/64
	POS5/1/1	3002::1/64		POS5/1/4	4002::2/64

Configuration procedure

1. Enable IPv6 forwarding, assign IPv6 addresses, and configure IPv6 unicast routing:

Enable IPv6 forwarding and assign the IP address and prefix length for each interface as per Figure 18. (Details not shown)

Configure the OSPFv3 protocol for interoperation among the routers in the IPv6 PIM-SM domain. Ensure the network-layer interoperation in the PIM-SM domain and enable dynamic update of routing information among the routers through a unicast routing protocol. (Details not shown)

2. Enable IPv6 multicast routing, IPv6 PIM-SM, and MLD:

# Enable IPv6 multicast routing on Router A, and enable IPv6 PIM-SM on each interface, and run MLDv2 on GigabitEthernet 3/1/1, which connects Router A to N1.

<RouterA> system-view

[RouterA] multicast ipv6 routing-enable

[RouterA] interface GigabitEthernet 3/1/1

[RouterA-GigabitEthernet3/1/1] mld enable

[RouterA-GigabitEthernet3/1/1] mld version 2

[RouterA-GigabitEthernet3/1/1] pim ipv6 sm

[RouterA-GigabitEthernet3/1/1] quit

[RouterA] interface serial 4/1/9/1:0

[RouterA-Serial4/1/9/1:0] pim ipv6 sm

[RouterA-Serial4/1/9/1:0] quit

[RouterA] interface pos 5/1/1

[RouterA-Pos5/1/1] pim ipv6 sm

[RouterA-Pos5/1/1] quit

3. Configure the IPv6 SSM group range:

# Configure the IPv6 SSM group range to be FF3E::/64 on Router A.

[RouterA] acl ipv6 number 2000

[RouterA-acl6-basic-2000] rule permit source ff3e:: 64

[RouterA-acl6-basic-2000] quit

[RouterA] pim ipv6

[RouterA-pim6] ssm-policy 2000

[RouterA-pim6] quit

The configuration on Router B, Router C, Router D and Router E is similar to that on Router A.

4. Verify the configuration:

# Display IPv6 PIM configuration information on Router A.

[RouterA] display pim ipv6 interface

Interface NbrCnt HelloInt DR-Pri DR-Address

GE3/1/1 0 30 1 1001::1

(local)

Ser4/1/9/1:0 1 30 1 1002::2

Pos5/1/1 1 30 1 1003::2

Assume that Host A needs to receive the information a specific IPv6 multicast source S (4001::100) sends to multicast group G (FF3E::101/64). Router A builds an SPT toward the multicast source. Routers on the SPT path (Router A and Router D) have generated an (S, G) entry, while Router E, which is not on the SPT path, does not have multicast routing entries. You can use the display pim ipv6 routing-table command to view the PIM routing table information on each router. For example:

# Display IPv6 PIM multicast routing table information on Router A.

[RouterA] display pim ipv6 routing-table

Total 0 (*, G) entry; 1 (S, G) entry

(4001::100, FF3E::101)

Protocol: pim-ssm, Flag:

UpTime: 00:00:11

Upstream interface: Serial4/1/9/1:0

Upstream neighbor: 1002::2

RPF prime neighbor: 1002::2

Downstream interface(s) information:

Total number of downstreams: 1

1: GigabitEthernet3/1/1

Protocol: mld, UpTime: 00:00:11, Expires: 00:03:25

# Display IPv6 PIM multicast routing table information on Router D.

[RouterD] display pim ipv6 routing-table

Total 0 (*, G) entry; 1 (S, G) entry

(4001::100, FF3E::101)

Protocol: pim-ssm, Flag: LOC

UpTime: 00:08:02

Upstream interface: GigabitEthernet3/1/1

Upstream neighbor: NULL

RPF prime neighbor: NULL

Downstream interface(s) information:

Total number of downstreams: 1

1: Serial4/1/9/1:0

Protocol: pim-ssm, UpTime: 00:08:02, Expires: 00:03:25

Troubleshooting IPv6 PIM

A multicast distribution tree cannot be built correctly

Symptom

None of the routers in the network (including routers directly connected with IPv6 multicast sources and receivers) have IPv6 multicast forwarding entries. That is, a multicast distribution tree cannot be built correctly and clients cannot receive IPv6 multicast data.

Analysis

· An IPv6 PIM routing entry is created based on an IPv6 unicast route, whichever IPv6 PIM mode is running. Multicast works only when unicast does.

· IPv6 PIM must be enabled on the RPF interface. An RPF neighbor must be an IPv6 PIM neighbor as well. If IPv6 PIM is not enabled on the RPF interface or the RPF neighbor, the establishment of a multicast distribution tree will surely fail, resulting in abnormal multicast forwarding.

· IPv6 PIM requires that the same IPv6 PIM mode (namely, DM or SM) must run on the entire network. Otherwise, the establishment of a multicast distribution tree will surely fail, resulting in abnormal multicast forwarding.

Solution

1. Use the display ipv6 routing-table command to verify that a unicast route to the IPv6 multicast source or the RP is available.

2. Use the display pim ipv6 interface command to verify the IPv6 PIM information on each interface, especially on the RPF interface. If IPv6 PIM is not enabled on the interface, use the pim ipv6 dm or pim ipv6 sm command to enable IPv6 PIM.

3. Use the display pim ipv6 neighbor command to verify that the RPF neighbor is an IPv6 PIM neighbor.

4. Verify that IPv6 PIM and MLD are enabled on the interfaces directly connecting to the IPv6 multicast source and to the receiver.

5. Use the display pim ipv6 interface verbose command to verify that the same PIM mode is enabled on the RPF interface and the corresponding interface of the RPF neighbor router.

6. Use the display current-configuration command to verify the IPv6 PIM mode information on each interface. Make sure that the same IPv6 PIM mode (IPv6 PIM-SM or IPv6 PIM-DM) is enabled on all routers.

IPv6 multicast data is abnormally terminated on an intermediate router

Symptom

An intermediate router can receive IPv6 multicast data successfully, but the data cannot reach the last-hop router. An interface on the intermediate router receives data but no corresponding (S, G) entry is created in the IPv6 PIM routing table.

Analysis

· When a router receives an IPv6 multicast packet, it decrements the hop limit value of the IPv6 multicast packet by 1 and recalculates the checksum value. The router then forwards the packet to all outgoing interfaces. If the multicast ipv6 minimum-hoplimit command is configured on the outgoing interfaces, the hop limit value of the packet must be larger than the configured minimum hop limit value. Otherwise, the packet will be discarded.

· If an IPv6 multicast forwarding boundary has been configured through the multicast ipv6 boundary command, any IPv6 multicast packet will be kept from crossing the boundary, and therefore no routing entry can be created in the IPv6 PIM routing table.

· In addition, the source-policy command filters received IPv6 multicast packets. If the IPv6 multicast data fails to pass the IPV6 ACL rule defined in this command, IPv6 PIM cannot create the route entry, either.

Solution

1. Use the display current-configuration command to check the minimum hop limit value for multicast forwarding. Increase the hop limit value or cancel the configuration of the multicast ipv6 minimum-hoplimit command on the interface.

2. Use the display current-configuration command to verify the IPv6 multicast forwarding boundary settings. Use the multicast ipv6 boundary command to change the IPv6 multicast forwarding boundary settings.

3. Use the display current-configuration command to verify the IPv6 multicast filter configuration. Change the IPv6 ACL rule defined in the source-policy command so that the source/group address of the IPv6 multicast data can pass ACL filtering.

RPs cannot join the SPT in IPv6 PIM-SM

Symptom

An RPT cannot be established correctly, or the RPs cannot join the SPT to the IPv6 multicast source.

Analysis

· As the core of an IPv6 PIM-SM domain, the RPs serves specific IPv6 multicast groups. Multiple RPs can coexist in a network. Make sure that the RP information on all routers is exactly the same, and a specific group is mapped to the same RP. Otherwise, IPv6 multicast will fail.

· In the case of the static RP mechanism, the same RP address must be configured on all the routers in the entire network, including static RPs, by means of the static RP command. Otherwise, IPv6 multicast will fail.

Solution

1. Use the display ipv6 routing-table command to verify that a route to the RP is available on each router.

2. Use the display pim ipv6 rp-info command to verify that the dynamic RP information is consistent on all routers. In case of inconsistent RP information, configure consistent RP address on all the routers.

3. Use the display pim ipv6 rp-info command to verify that the same RP address has been configured on all the routers throughout the network.

RPT cannot be established or a source cannot register in IPv6 PIM-SM

Symptom

C-RPs cannot unicast advertise messages to the BSR. The BSR does not advertise bootstrap messages containing C-RP information and has no unicast route to any C-RP. An RPT cannot be established correctly, or the DR cannot perform source registration with the RP.

Analysis

· C-RPs periodically send advertisement messages to the BSR by unicast. If a C-RP does not have a route to the BSR, the BSR cannot receive the advertisements from the C-RP and the bootstrap messages of the BSR do not contain the information about that C-RP.

· The RP is the core of an IPv6 PIM-SM domain. Make sure that the RP information on all routers is exactly the same, a specific group is mapped to the same RP, and a unicast route is available to the RP.

Solution

1. Use the display ipv6 routing-table command to verify that routes to the RP and the BSR are available on each router, and that a route between the RP and the BSR is available. Make sure that each C-RP has a unicast route to the BSR, the BSR has a unicast route to each C-RP, and all the routers in the entire network have a unicast route to the RP.

2. IPv6 PIM-SM needs the support of the RP and BSR. Use the display pim ipv6 bsr-info command to verify that the BSR information exists on each router, and then use the display pim ipv6 rp-info command to verify that the RP information is correct on each router.

3. Use the display pim ipv6 neighbor command to verify that normal neighboring relationships have been established among the routers.

07-IP Multicast Configuration Guide

IPv6 PIM overview

IPv6 PIM-DM overview

SPT establishment

Graft

IPv6 PIM-SM overview

Embedded RP

RPT establishment

Switchover to SPT

Assert

Neighbor discovery

RP discovery

DF election

Bidirectional RPT building

IPv6 administrative scoping overview

Division of IPv6 PIM-SM domains

Relationship between IPv6 admin-scope zones and the IPv6 global scope zone

Neighbor discovery

DR election

SPT building

Enabling state-refresh capability

IPv6 PIM-SM configuration task list

Configuring C-RP timers globally

Configuring C-BSR parameters globally

Disabling BSM semantic fragmentation

Configuring IPv6 administrative scoping

Configuring C-BSRs for IPv6 admin-scope zones

Configuring IPv6 multicast source registration

Configuring SPT switchover

Configuring IPv6 BIDIR-PIM

Enabling IPv6 BIDIR-PIM

Configuring an IPv6 BIDIR-PIM domain border

Configuring the IPv6 SSM group range

Configuring hello options globally

Configuring hello options on an interface

Configuring IPv6 PIM common timers globally

Configuring IPv6 PIM common timers on an interface

Configuring join/prune message sizes

Network requirements

Configuration procedure

IPv6 PIM-SM non-scoped zone configuration example

Network requirements

Configuration procedure

IPv6 PIM-SM admin-scope zone configuration example

Network requirements

Configuration procedure

Network requirements

Configuration procedure

Network requirements

Configuration procedure

Troubleshooting IPv6 PIM

Symptom

Analysis

Solution

Symptom

Analysis

Solution

Symptom

Analysis

Solution

Symptom

Analysis

Solution

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