This manual chiefly focuses on the IP multicast technology and device operations. Unless otherwise stated, the term “multicast” in this document refers to IP multicast.

Introduction to Multicast

As a technique coexisting with unicast and broadcast, the multicast technique effectively addresses the issue of point-to-multipoint data transmission. By allowing high-efficiency point-to-multipoint data transmission over a network, multicast greatly saves network bandwidth and reduces network load.

With the multicast technology, a network operator can easily provide new value-added services, such as live Webcasting, Web TV, distance learning, telemedicine, Web radio, real-time videoconferencing, and other bandwidth- and time-critical information services.

Comparison of Information Transmission Techniques

Unicast

In unicast, the information source (Source in the figure) needs to send a separate copy of information to each host (Receiver in the figure) that wants the information, as shown in Figure 1-1.

Figure 1-1 Unicast transmission

Assume that Host B, Host D and Host E need the information. A separate transmission channel needs to be established from the information source to each of these hosts.

In unicast transmission, the traffic transmitted over the network is proportional to the number of hosts that need the information. If a large number of users need the information, the information source needs to send a copy of the same information to each of these users. This means a tremendous pressure on the information source and the network bandwidth.

As we can see from the information transmission process, unicast is not suitable for batch transmission of information.

Broadcast

In broadcast, the information source sends information to all hosts on the subnet, even if some hosts do not need the information, as shown in Figure 1-2.

Figure 1-2 Broadcast transmission

Assume that only Host B, Host D, and Host E need the information. If the information is broadcast to the subnet, Host A and Host C also receive it. In addition to information security issues, this also causes traffic flooding on the same subnet.

Therefore, broadcast is disadvantageous in transmitting data to specific hosts; moreover, broadcast transmission is a significant waste of network resources.

Multicast

As discussed above, unicast and broadcast techniques are unable to provide point-to-multipoint data transmissions with the minimum network consumption.

Multicast can well solve this problem. When some hosts on the network need multicast information, the information sender, or multicast source, sends only one copy of the information. Multicast distribution trees are built through multicast routing protocols, and the packets are replicated only on nodes where the trees branch. Figure 1-3 shows the delivery of a data stream to receiver hosts through multicast.

Figure 1-3 Multicast transmission

The multicast source (Source in the figure) sends only one copy of the information to a multicast group. Host B, Host D and Host E, which are receivers of the information, need to join the multicast group. The routers on the network duplicate and forward the information based on the distribution of the group members. Finally, the information is correctly delivered to Host B, Host D, and Host E.

To sum up, the advantages of multicast are summarized as follows:

l Over unicast: As multicast traffic flows to the node the farthest possible from the source before it is replicated and distributed, an increase of the number of hosts will not increase the load of the source and will not remarkably add to network resource usage.

l Over broadcast: As multicast data is sent only to the receivers that need it, multicast uses the network bandwidth reasonably and enhances network security. In addition, data broadcast is confined to the same subnet, while multicast is not.

Features of Multicast

Multicast has the following features:

l A multicast group is a multicast receiver set identified by an IP multicast address. Hosts join a multicast group to become members of the multicast group, before they can receive the multicast data addressed to that multicast group. Typically, a multicast source does not need to join a multicast group.

l An information sender is referred to as a multicast source (Source in Figure 1-3). A multicast source can send data to multiple multicast groups at the same time, and multiple multicast sources can send data to the same multicast group at the same time.

l All hosts that have joined a multicast group become members of the multicast group (Receiver in Figure 1-3). The group memberships are dynamic. Hosts can join or leave multicast groups at any time. Multicast groups are not subject to geographic restrictions.

l Routers or Layer 3 switches that support Layer 3 multicast are called multicast routers or Layer 3 multicast devices. In addition to providing the multicast routing function, a multicast router can also manage multicast group memberships on stub subnets with attached group members. A multicast router itself can be a multicast group member.

For a better understanding of the multicast concept, you can assimilate multicast transmission to the transmission of TV programs, as shown in Table 1-1.

Table 1-1 An analogy between TV transmission and multicast transmission

TV transmission	Multicast transmission
A TV station transmits a TV program through a channel.	A multicast source sends multicast data to a multicast group.
A user tunes the TV set to the channel.	A receiver joins the multicast group.
The user starts to watch the TV program transmitted by the TV station via the channel.	The receiver starts to receive the multicast data that the source is sending to the multicast group.
The user turns off the TV set or tunes to another channel.	The receiver leaves the multicast group or joins another group.

Common Notations in Multicast

Two notations are commonly used in multicast:

l (*, G): Indicates a rendezvous point tree (RPT), or a multicast packet that any multicast source sends to multicast group G. Here “*” represents any multicast source, while “G” represents a specific multicast group.

l (S, G): Indicates a shortest path tree (SPT), or a multicast packet that multicast source S sends to multicast group G. Here “S” represents a specific multicast source, while “G” represents a specific multicast group.

Advantages and Applications of Multicast

Advantages of multicast

Advantages of the multicast technique include:

l Enhanced efficiency: reduces the CPU load of information source servers and network devices.

l Optimal performance: reduces redundant traffic.

l Distributive application: enables point-to-multipoint applications at the price of minimum network resources.

Applications of multicast

Applications of the multicast technique include:

l Multimedia and streaming applications, such as Web TV, Web radio, and real-time video/audio conferencing.

l Communication for training and cooperative operations, such as distance learning and telemedicine.

l Data warehouse and financial applications (stock quotes).

l Any other point-to-multipoint data distribution application.

Multicast Models

Based on how the receivers treat the multicast sources, there are three multicast models: any-source multicast (ASM), source-filtered multicast (SFM), and source-specific multicast (SSM).

ASM model

In the ASM model, any sender can send information to a multicast group as a multicast source, and numbers of receivers can join a multicast group identified by a group address and obtain multicast information addressed to that multicast group. In this model, receivers are not aware of the position of multicast sources in advance. However, they can join or leave the multicast group at any time.

SFM model

The SFM model is derived from the ASM. From the view of a sender, the two models have the same multicast membership architecture.

The SFM model functionally extends the ASM model: In the SFM model, the upper layer software checks the source address of received multicast packets and permits or denies multicast traffic from specific sources. Therefore, receivers can receive the multicast data from only part of the multicast sources. From the view of a receiver, multicast sources are not all valid: they are filtered.

SSM model

In the practical life, users may be interested in the multicast data from only certain multicast sources. The SSM model provides a transmission service that allows users to specify the multicast sources they are interested in at the client side.

The radical difference between the SSM model and the ASM model is that in the SSM model, receivers already know the locations of the multicast sources by some other means. In addition, the SSM model uses a multicast address range that is different from that of the ASM/SFM model, and dedicated multicast forwarding paths are established between receivers and the specified multicast sources.

Multicast Architecture

IP multicast addresses the following questions:

l Where should the multicast source transmit information to? (multicast addressing)

l What receivers exist on the network? (host registration)

l Where is the multicast source the receivers need to receive multicast data from? (multicast source discovery)

l How should information be transmitted to the receivers? (multicast routing)

IP multicast falls in the scope of end-to-end service. The multicast architecture involves the following four parts:

l Addressing mechanism: Information is sent from a multicast source to a group of receivers through a multicast address.

l Host registration: Receiver hosts are allowed to join and leave multicast groups dynamically. This mechanism is the basis for group membership management.

l Multicast routing: A multicast distribution tree (namely a forwarding path tree for multicast data on the network) is constructed for delivering multicast data from a multicast source to receivers.

l Multicast applications: A software system that supports multicast applications, such as video conferencing, must be installed on multicast sources and receiver hosts, and the TCP/IP stack must support reception and transmission of multicast data.

Multicast Addresses

To allow communication between multicast sources and multicast group members, network-layer multicast addresses, namely, multicast IP addresses must be provided. In addition, a technique must be available to map multicast IP addresses to link-layer multicast MAC addresses.

IP multicast addresses

Internet Assigned Numbers Authority (IANA) assigned the Class D address space (224.0.0.0 to 239.255.255.255) for IPv4 multicast. The specific address blocks and usages are shown in Table 1-2.

Table 1-2 Class D IP address blocks and description

Address block	Description
224.0.0.0 to 224.0.0.255	Reserved permanent group addresses. The IP address 224.0.0.0 is reserved, and other IP addresses can be used by routing protocols and for topology searching, protocol maintenance, and so on. Common permanent group addresses are listed in Table 1-3. A packet destined for an address in this block will not be forwarded beyond the local subnet regardless of the Time to Live (TTL) value in the IP header.
224.0.1.0 to 238.255.255.255	Globally scoped group addresses. This block includes two types of designated group addresses: l 232.0.0.0/8: SSM group addresses, and l 233.0.0.0/8: Glop group addresses.
239.0.0.0 to 239.255.255.255	Administratively scoped multicast addresses. These addresses are considered to be locally rather than globally unique, and can be reused in domains administered by different organizations without causing conflicts. For details, refer to RFC 2365.

l The membership of a group is dynamic. Hosts can join or leave multicast groups at any time.

l “Glop” is a mechanism for assigning multicast addresses between different autonomous systems (ASs). By filling an AS number into the middle two bytes of 233.0.0.0, you get 255 multicast addresses for that AS. For more information, refer to RFC 2770.

Table 1-3 Some reserved multicast addresses

Address	Description
224.0.0.1	All systems on this subnet, including hosts and routers
224.0.0.2	All multicast routers on this subnet
224.0.0.3	Unassigned
224.0.0.4	Distance Vector Multicast Routing Protocol (DVMRP) routers
224.0.0.5	Open Shortest Path First (OSPF) routers
224.0.0.6	OSPF designated routers/backup designated routers
224.0.0.7	Shared Tree (ST) routers
224.0.0.8	ST hosts
224.0.0.9	Routing Information Protocol version 2 (RIPv2) routers
224.0.0.11	Mobile agents
224.0.0.12	Dynamic Host Configuration Protocol (DHCP) server/relay agent
224.0.0.13	All Protocol Independent Multicast (PIM) routers
224.0.0.14	Resource Reservation Protocol (RSVP) encapsulation
224.0.0.15	All Core-Based Tree (CBT) routers
224.0.0.16	Designated Subnetwork Bandwidth Management (SBM)
224.0.0.17	All SBMs
224.0.0.18	Virtual Router Redundancy Protocol (VRRP)

Ethernet multicast MAC addresses

When a unicast IP packet is transmitted over Ethernet, the destination MAC address is the MAC address of the receiver. When a multicast packet is transmitted over Ethernet, however, the destination address is a multicast MAC address because the packet is directed to a group formed by a number of receivers, rather than to one specific receiver.

As defined by IANA, the high-order 24 bits of an IPv4 multicast MAC address are 0x01005E, bit 25 is 0, and the low-order 23 bits are the low-order 23 bits of a multicast IPv4 address. The IPv4-to-MAC mapping relation is shown in Figure 1-4.

Figure 1-4 IPv4-to-MAC address mapping

The high-order four bits of a multicast IPv4 address are 1110, indicating that this address is a multicast address, and only 23 bits of the remaining 28 bits are mapped to a MAC address, so five bits of the multicast IPv4 address are lost. As a result, 32 multicast IPv4 addresses map to the same MAC address. Therefore, in Layer 2 multicast forwarding, a device may receive some multicast data addressed for other IPv4 multicast groups, and such redundant data needs to be filtered by the upper layer.

Multicast Protocols

Generally, we refer to IP multicast working at the network layer as Layer 3 multicast and the corresponding multicast protocols as Layer 3 multicast protocols, which include IGMP, PIM, MSDP, and MBGP; we refer to IP multicast working at the data link layer as Layer 2 multicast and the corresponding multicast protocols as Layer 2 multicast protocols, which include IGMP Snooping, and multicast VLAN.

Layer 3 multicast protocols

Layer 3 multicast protocols include multicast group management protocols and multicast routing protocols. Figure 1-5 describes where these multicast protocols are in a network.

Figure 1-5 Positions of Layer 3 multicast protocols

1) Multicast management protocols

Typically, the internet group management protocol (IGMP) is used between hosts and Layer 3 multicast devices directly connected with the hosts. These protocols define the mechanism of establishing and maintaining group memberships between hosts and Layer 3 multicast devices.

2) Multicast routing protocols

A multicast routing protocol runs on Layer 3 multicast devices to establish and maintain multicast routes and forward multicast packets correctly and efficiently. Multicast routes constitute a loop-free data transmission path from a data source to multiple receivers, namely, a multicast distribution tree.

In the ASM model, multicast routes come in intra-domain routes and inter-domain routes.

l An intra-domain multicast routing protocol is used to discover multicast sources and build multicast distribution trees within an AS so as to deliver multicast data to receivers. Among a variety of mature intra-domain multicast routing protocols, protocol independent multicast (PIM) is a popular one. Based on the forwarding mechanism, PIM comes in two modes – dense mode (often referred to as PIM-DM) and sparse mode (often referred to as PIM-SM).

l An inter-domain multicast routing protocol is used for delivery of multicast information between two ASs. So far, mature solutions include multicast source discovery protocol (MSDP) and multicast border gateway protocol (MBGP). MSDP is used to propagate multicast source information among different ASs, while MBGP, an extension of the Multi-protocol Border Gateway Protocol (MP-BGP), is used for exchanging multicast routing information among different ASs.

For the SSM model, multicast routes are not divided into inter-domain routes and intra-domain routes. Since receivers know the position of the multicast source, channels established through PIM-SM are sufficient for multicast information transport.

Layer 2 multicast protocols

Layer 2 multicast protocols include IGMP Snooping and multicast VLAN. Figure 1-6 shows where these protocols are in the network.

Figure 1-6 Position of Layer 2 multicast protocols

1) IGMP Snooping

Running on Layer 2 devices, Internet Group Management Protocol Snooping (IGMP Snooping) is multicast constraining mechanisms that manage and control multicast groups by listening to and analyzing IGMP messages exchanged between the hosts and Layer 3 multicast devices, thus effectively controlling the flooding of multicast data in a Layer 2 network.

2) Multicast VLAN

In the traditional multicast-on-demand mode, when users in different VLANs on a Layer 2 device need multicast information, the upstream Layer 3 device needs to forward a separate copy of the multicast data to each VLAN of the Layer 2 device. With the multicast VLAN feature enabled on the Layer 2 device, the Layer 3 multicast device needs to send only one copy of multicast to the multicast VLAN on the Layer 2 device. This avoids waste of network bandwidth and extra burden on the Layer 3 device.

Multicast Packet Forwarding Mechanism

In a multicast model, a multicast source sends information to the host group identified by the multicast group address in the destination address field of IP multicast packets. Therefore, to deliver multicast packets to receivers located in different parts of the network, multicast routers on the forwarding path usually need to forward multicast packets received on one incoming interface to multiple outgoing interfaces. Compared with a unicast model, a multicast model is more complex in the following aspects.

l To ensure multicast packet transmission in the network, unicast routing tables or multicast routing tables (for example, the MBGP routing table) specially provided for multicast must be used as guidance for multicast forwarding.

l To process the same multicast information from different peers received on different interfaces of the same device, every multicast packet is subject to a reverse path forwarding (RPF) check on the incoming interface. The result of the RPF check determines whether the packet will be forwarded or discarded. The RPF check mechanism is the basis for most multicast routing protocols to implement multicast forwarding.

Multicast Modes of ONU Devices

Multicast modes of an ONU device can be remotely configured on an OLT device through extended OAM, thus controlling and managing the multicast services. An ONU device can operate in two multicast modes:

l IGMP snooping mode: The ONU device runs IGMP snooping and dynamically manages multicast group memberships using the IGMP report, leave, and query messages.

l Multicast control mode: When the ONU device operates in the multicast control mode, the OLT device controls user access to the ONU device based on the user ID carried in the IGMP control messages and controls multicast forwarding on the ONU device using the extended OAM messages.

2 Multicast Mode Configuration

l This chapter chiefly focuses on the multicast modes of the ONU devices. For details about IGMP snooping, refer to IGMP Snooping Configuration.

l Configuration of the multicast mode for an ONU device performed on an OLT device takes effect only if multicast is supported for the ONU device.

Overview

ONU devices can operate in two multicast modes, IGMP snooping mode and multicast control mode.

IGMP Snooping Mode

In the IGMP snooping mode, an ONU listens to the IGMP report, leave, and query messages exchanged between hosts and the multicast router, establishes mappings between ports and multicast MAC addresses by adding entries to the IGMP snooping forwarding table, and then forwards multicast data to the corresponding ports attached with multicast members based on these mappings. The OLT device can implement simple control of multicast access through the multicast VLAN control on the UNI ports of the ONU device.

Multicast control mode

Principle of the multicast control mode:

1) OLT-side functions

l The OLT side maintains a user multicast service access control table to centrally manage user multicast service access rights.

l The OLT identifies users through user LLIDs and the VLAN tags (consistent with UNI port numbers) carried in uplink IGMP report messages, and determines whether a user has the right to access the requested multicast service and, if yes, the related parameters.

l The OLT uses extended multicast control OAM packets to send the ONU the user's access right to the multicast channel, allowing the ONU to forward or shut off the multicast traffic for the user. The network management system at the OLT side centrally manages the multicast access control. The OLT governs, while an ONU executes, multicast right management.

2) ONU-side functions

l The ONU side maintains a table for multicast address filtering and multicast forwarding. It performs flow control only for the current multicast service on the ONU.

l The ONU adds VLAN tags (A UNI port number is used as the VLAN tag. For example, the packets received on UNI 1 are tagged with VLAN 1.) to the IGMP report messages without VLAN tags to identify users, and transparently sends the messages to the OLT. Then the ONU adds or deletes the group address filtering and multicast forwarding entries on the ONU based on the multicast control OAM packets (containing a series of multicast control entries) delivered by the OLT, and forwards or shuts off the multicast traffic accordingly.

Multicast Mode Configuration Task List

You can use the OLT to remotely configure the aging timer of the ONU router port, the aging timer of multicast group member ports, the query response timer, and IGMP membership report suppression.

For information about the router port, multicast group member port, and aging timers, refer to Basic Concepts in IGMP Snooping.

Table 2-1 Complete these tasks to configure the multicast mode for the ONU device.

Task		Remarks
Prerequisites for multicast mode configuration		Required
Configuring the IGMP snooping mode	Configuring the IGMP Snooping Mode for the ONU Device	Optional
	Assigning a UNI Port to the Specified Multicast VLAN	Required
	Configuring the Port Aging Timer	Optional
	Configuring Fast-Leave Processing for a UNI	Optional
	Configuring the IGMP Query Response Timer	Optional
	Configuring IGMP Report Suppression	Optional
	Configuring the Maximum Number of Multicast Channels on a UNI	Optional
	Removing the VLAN Tag of Downlink Multicast Packets on a UNI Port	Optional
Configuring the Multicast control mode	Configuring the Multicast Control Mode for the ONU Device	Required
	Configuring the Aging Timer for Member Ports	Optional
	Configure Multicast Channel Access on a UNI	Required
	Removing the VLAN Tag of Downlink Multicast Packets on a UNI Port	Optional

Prerequisites for multicast mode configuration

Configure multicast VLANs on the OLT device to separate multicast services. Each multicast VLAN corresponds to a multicast channel or channel group. A channel group is a group of multicast channels requiring the same access right. Each multicast channel or channel group belongs to only one multicast VLAN at a time.

The configuration of a multicast IP address-to-multicast VLAN correspondence is used to add multicast address(es) to a multicast VLAN. Upon receiving an IGMP report message, the OLT determines whether the multicast IP address contained in the message belongs to the multicast VLAN. If yes, the OLT generates a multicast forwarding entry in the multicast VLAN of the multicast IP address; otherwise, the OLT directly discards the message.

Follow these steps to complete the prerequisites for multicast mode configuration:

To do...	Use the command...	Remarks
Enter system view	system-view	—
Enter FTTH view	ftth	—
Add multicast address(es) to a multicast VLAN	multicast vlan-id vlan-id dest-ip ip-address-list	Required
Return to system view	quit	—
Enable IGMP snooping globally	igmp-snooping	Required Disabled by default
Return to system view	quit	—
Enter VLAN view of a multicast VLAN	vlan vlan-id	—
Enable IGMP snooping	igmp-snooping enable	Required Disabled by default
Drop unknown multicast traffic	igmp-snooping drop-unknown	Optional

For details about the igmp snooping, igmp-snooping enable, and igmp-snooping drop-unknow commands, refer to Multicast Commands.

Configuring the IGMP snooping mode

Before configuring the IGMP snooping mode, complete the tasks Prerequisites for multicast mode configuration and prepare the following data:

l Aging time for dynamic router ports on the ONU device.

l Aging time for dynamic member ports on the ONU device.

l Maximum response time to IGMP general queries.

l Maximum number of multicast channels requested by the users connected to a UNI at the same time.

Configuring the IGMP Snooping Mode for the ONU Device

Follow these steps to configure the IGMP snooping mode for the ONU device

To do...	Use the command...	Remarks
Enter system view	system-view	—
Enter ONU port view	interface onu interface-number	—
Configure the multicast mode of the ONU as IGMP snooping	multicast-mode igmp-snooping	Optional By default, the multicast mode of the ONU is IGMP Snooping.

Assigning a UNI Port to the Specified Multicast VLAN

Follow these steps to assign the UNI port to the specified multicast VLAN

To do...	Use the command...	Remarks
Enter system view	system-view	—
Enter ONU port view	interface onu interface-number	—
Add a UNI to the specified multicast VLAN(s)	uni uni-number multicast vlan { vlan-id } & <1-50>	Required

Configuring the Port Aging Timer

If an ONU receives no IGMP general queries or PIM hello messages on a dynamic router port, the ONU removes the port from the router port list when the aging timer of the port expires.

If the ONU receives no IGMP reports for a multicast group on a dynamic member port, the ONU removes the port from the outgoing port list of the forwarding table entry for that multicast group when the aging timer of the port for that group expires.

If multicast group memberships change frequently, you can set a relatively small value for the dynamic member port aging timer, and vice versa.

Follow these steps to configure the aging timer for the dynamic ports on the ONU device

To do...	Use the command...	Remarks
Enter system view	system-view	—
Enter ONU port view	interface onu interface-number	—
Configure the aging timer of the router port	onu-protocol igmp-snooping router-aging-time interval	Optional 105 seconds by default
Configure the aging timer of the multicast member port	onu-protocol igmp-snooping host-aging-time interval	Optional 260 seconds by default

The onu-protocol igmp-snooping router-aging-time and onu-protocol igmp-snooping host-aging-time commands are applicable to only H3C’s ONU devices.

Configuring Fast-Leave Processing for a UNI

With the fast-leave processing feature enabled, when the ONU receives an IGMP leave message from a host announcing its leaving a multicast group, the ONU immediately deletes that port from the outgoing port list of the forwarding table. After that, when receiving IGMP group-specific queries for that multicast group, the ONU will not forward them to that port.

If only one host is attached to a port on the ONU, fast-leave processing helps improve bandwidth and resource usage.

Follow these steps to configure fast-leave processing for a UNI:

To do...	Use the command...	Remarks
Enter system view	system-view	—
Enter ONU port view	interface onu interface-number	—
Enable fast-leave processing on a UNI	uni uni-number igmp-snooping fast-leave	Required By default, fast-leave processing is disabled on a UNI.

Configuring the IGMP Query Response Timer

Follow these steps to configure the IGMP query response timer for the ONU device

To do...	Use the command...	Remarks
Enter system view	system-view	—
Enter ONU port view	interface onu interface-number	—
Configure the query-response timer	onu-protocol igmp-snooping max-response-time interval	Optional By default, the maximum response time to group-specific queries is 10 seconds.

The onu-protocol igmp-snooping max-response-time command is applicable to only H3C’s ONU devices.

Configuring IGMP Report Suppression

When an ONU receives an IGMP membership report from a multicast group member, the ONU forwards the message to the OLT. Thus, when multiple members of a multicast group are attached to the ONU, the OLT will receive duplicate IGMP reports from these members. The same situation occurs when multiple members send leave messages to leave a multicast group.

With the IGMP report suppression function enabled, within each query cycle, the ONU forwards only the first IGMP report of a multicast group to the OLT and will not forward the subsequent IGMP reports from the same multicast group to the OLT. This helps to reduce the number of packets being transmitted over the network.

Follow these steps to configure IGMP report suppression

To do...	Use the command...	Remarks
Enter system view	system-view	—
Enter ONU port view	interface onu interface-number	—
Enable IGMP membership report suppression	onu-protocol igmp-snooping report-aggregation enable	Optional Disabled by default
Enable IGMP leave report suppression	onu-protocol igmp-snooping leave-aggregation enable	Optional Enabled by default

The onu-protocol igmp-snooping report-aggregation enable and onu-protocol igmp-snooping leave-aggregation enable commands are applicable to only H3C’s ONU devices.

Configuring the Maximum Number of Multicast Channels on a UNI

The number of multicast channels requested by the users connected to a UNI can be controlled by configuring the maximum number of multicast channels a UNI port can join, thus controlling the traffic on the UNI port.

Follow these steps to configure the maximum number of multicast channels on a UNI port.

To do...	Use the command...	Remarks
Enter system view	system-view	—
Enter ONU port view	interface onu interface-number	—
Configure the number of multicast channels on the specified UNI	uni uni-number multicast-group-number number	Optional By default, the users connected to a UNI can access 64 multicast channels at the same time.

Removing the VLAN Tag of Downlink Multicast Packets on a UNI Port

Follow these steps to remove the VLAN tag of downlink multicast packets on a UNI port

To do...	Use the command...	Remarks
Enter system view	system-view	—
Enter ONU port view	interface onu interface-number	—
Remove the VLAN tag of the downlink multicast flow on the UNI port	uni uni-number multicast-strip-tag enable	Optional By default, a UNI does not remove the VLAN tag of the downlink multicast flow.

Configuring the Multicast control mode

Before configuring the multicast control mode, complete the tasks Prerequisites for multicast mode configuration and prepare the following data:

l Aging time for dynamic member ports

l Number of requested channels

l Preview time

Configuring the Multicast Control Mode for the ONU Device

Follow these steps to configure the multicast control mode for the ONU device.

To do...	Use the command...	Remarks
Enter system view	system-view	—
Enter ONU port view	interface onu interface-number	—
Configure the multicast mode of the ONU as the multicast control mode	multicast-mode multicast-control	Required By default, the multicast mode of the ONU is IGMP Snooping.

Configuring the Aging Timer for Member Ports

Follow these steps to configure the aging timer for member ports under the multicast control mode

To do...	Use the command...	Remarks
Enter system view	system-view	—
Enter ONU port view	interface onu interface-number	—
Configure the aging timer of the multicast group members in the multicast control mode	multicast-control host-aging-time host-aging-time	Optional 260 seconds by default

Configure Multicast Channel Access on a UNI

Follow these steps to configure the access to multicast channels on the UNI port.

To do...	Use the command...	Remarks
Enter system view	system-view	—
Enter ONU port view	interface onu interface-number	—
Configure the access to multicast channels on the specified UNI	uni uni-number multicast-control multicast-address { multicast-address [ to multicast-address ] } &<1-10> [ source-ip ip-address [ to ip-address ] ] rule { deny \| permit [ channel-limit channel-number ] \| preview time-slice preview-time [ preview-interval interval-time \| preview-times preview-times [ reset-interval reset-interval-time ] ]* }	Required

Removing the VLAN Tag of Downlink Multicast Packets on a UNI Port

VLAN tags of downlink multicast packets on a UNI port are removed in the same way for both the multicast control mode and IGMP snooping mode. For details, see Removing the VLAN Tag of Downlink Multicast Packets on a UNI Port.

Displaying and Maintaining the Multicast Modes for ONU Devices

To do...	Use the command...	Remarks
Display the IGMP snooping mode information	display onu-protocol igmp-snooping	Available in ONU port view To display the information of an ONU, make sure the ONU is online.
Display multicast control information	display epon-multicast information
Clear the statistics information about the packets on an ONU port	reset counters interface interface-type interface-number	Available in user view

l Use the reset command in user view to clear the multicast group information. For details about the reset counters interface command, refer to Port Commands.

l The display onu-protocol igmp-snooping command is applicable to only H3C’s ONU devices.

Multicast Configuration Example

Multicast Configuration Example (in IGMP Snooping Mode)

Network requirements

l Connect GigabitEthernet1/1/1 of the S3600 series EPON OLT switch with a multicast source, and connect port OLT 1/0/1 of the OLT with an ONU, which is bound to ONU 1/0/1:1, through an optical splitter. Attach two hosts, User 1 and User 2, to ports UNI 1 and UNI 2 respectively.

l It is required that User 1 has access to channels from 225.1.2.1 to 225.1.2.255, and User 2 has access to channels from 225.1.3.1 to 225.1.3.255.

Network diagram

Figure 2-2 Network diagram for multicast configuration (in IGMP snooping mode)

Configuration procedure

Prior configurations for the OLT and ONU devices are required to ensure that the ONU devices can succeed in registering with the OLT. For details, see EPON-OLT Configuration.

# Map the multicast addresses to multicast VLANs.

<Sysname> system-view

[Sysname] ftth

[Sysname-ftth] multicast vlan-id 1002 dest-ip 225.1.2.1 to 225.1.2.255

[Sysname-ftth] multicast vlan-id 1003 dest-ip 225.1.3.1 to 225.1.3.255

[Sysname-ftth] quit

# Enable IGMP snooping globally.

[Sysname] igmp-snooping

[Sysname-igmp-snooping] quit

# Enable IGMP snooping in VLAN 1002 and VLAN 1003.

[Sysname] vlan 1002

[Sysname-vlan1002] igmp-snooping enable

[Sysname-vlan1002] quit

[Sysname] vlan 1003

[Sysname-vlan1003] igmp-snooping enable

[Sysname-vlan1003] quit

# Configure the multicast mode of the ONU as IGMP snooping.

[Sysname] interface onu 1/0/1:1

[Sysname-Onu1/0/1:1] multicast-mode igmp-snooping

# Assign UNI 1 to multicast VLAN 1002 and UNI 2 to multicast VLAN 1003, and configure the ONU as a Trunk port (to allow the packets of all the VLANs to pass through the port).

[Sysname-Onu1/0/1:1] uni 1 multicast vlan 1002

[Sysname-Onu1/0/1:1] uni 2 multicast vlan 1003

[Sysname-Onu1/0/1:1] port link-type trunk

# Configure UNI 1 and UNI 2 to remove the multicast VLAN tags from downlink multicast packets.

[Sysname-Onu1/0/1:1] uni 1 multicast-strip-tag enable

[Sysname-Onu1/0/1:1] uni 2 multicast-strip-tag enable

[Sysname-Onu1/0/1:1] quit

# Configure the link type of OLT 1/0/1 as hybrid, allow the packets of VLAN 1002 and VLAN 1003 to pass through OLT 1/0/1, and add tags to the VLAN 1002 and VLAN 1003 packets sent by OLT 1/0/1.

[Sysname] interface olt 1/0/1

[Sysname-Olt1/0/1] port link-type hybrid

[Sysname-Olt1/0/1] port hybrid vlan 1002 1003 tagged

# Configure GigabitEthernet1/1/1 as a Trunk port, and permit the packets of VLAN 1002 and VLAN 1003 to pass.

[Sysname] interface gigabitEthernet1/1/1

[Sysname-GigabitEthernet1/1/1] port link-type trunk

[Sysname-GigabitEthernet1/1/1] port trunk permit vlan 1002 1003

Multicast Configuration Example (in Multicast Control Mode)

Network requirements

Connect GigabitEthernet1/1/1 of the switch with a multicast source, and connect port OLT 1/0/1 of the OLT with an ONU, which is bound to ONU 1/0/1:1, through an optical splitter. Attach two hosts, User 1 and User 2, to ports UNI 1 and UNI 2 respectively.

It is required that User 1 and User 2 have different access rights to Channel 1 (225.1.1.1) and Channel 1 (225.1.2.1):

l User 1 has full access to Channel 1 and 60-second preview access to Channel 2.

l User 2 has access to Channel 2 only.

Network diagram

Figure 2-3 Network diagram for multicast configuration (in multicast control mode)

Configuration procedure

Prior configurations for the OLT and ONU devices are required to ensure that the ONU devices can succeed in registering with the OLT. For details, see EPON-OLT Configuration.

# Map the multicast addresses to multicast VLANs.

<Sysname> system-view

[Sysname] ftth

[Sysname-ftth] multicast vlan-id 1002 dest-ip 225.1.1.1

[Sysname-ftth] multicast vlan-id 1003 dest-ip 225.1.2.1

[Sysname-ftth] quit

# Enable IGMP snooping globally.

[Sysname] igmp-snooping

[Sysname-igmp-snooping] quit

# Enable IGMP snooping in VLAN 1002 and VLAN 1003.

[Sysname] vlan 1002

[Sysname-vlan1002] igmp-snooping enable

[Sysname-vlan1002] vlan 1003

[Sysname-vlan1003] igmp-snooping enable

[Sysname-vlan1003] quit

# Configure the multicast mode of the ONU as the multicast control mode.

[Sysname] interface onu 1/0/1:1

[Sysname-Onu1/0/1:1] multicast-mode multicast-control

# Configure UNI 1 to allow the user attached to it to access Channel 1 and to preview Channel 2 for only 60 seconds, and configure the port to remove the multicast VLAN tags from downlink multicast packets.

[Sysname-Onu1/0/1:1] uni 1 multicast-control multicast-address 225.1.1.1 rule permit

[Sysname-Onu1/0/1:1] uni 1 multicast-control multicast-address 225.1.2.1 rule preview time-slice 1

[Sysname-Onu1/0/1:1] uni 1 multicast-strip-tag enable

# Configure UNI 2 to allow the user attached to it to access Channel 2 only, and configure the port to remove the multicast VLAN tags from downlink multicast packets.

[Sysname-Onu1/0/1:1] uni 2 multicast-control multicast-address 225.1.1.1 rule deny

[Sysname-Onu1/0/1:1] uni 2 multicast-control multicast-address 225.1.2.1 rule permit

[Sysname-Onu1/0/1:1] uni 2 multicast-strip-tag enable

# Configure the ONU port as a Trunk port (to allow the packets of all the VLANs to pass through the port).

[Sysname-Onu1/0/1:1] port link-type trunk

# Configure the link type of OLT 1/0/1 as hybrid, allow the packets of VLAN 1002 and VLAN 1003 to pass through OLT 1/0/1, and add tags to the VLAN 1002 and VLAN 1003 packets sent by OLT 1/0/1.

[Sysname] interface olt 1/0/1

[Sysname-Olt1/0/1] port link-type hybrid

[Sysname-Olt1/0/1] port hybrid vlan 1002 1003 tagged

# Configure Ethernet 2/0/1 as a Trunk port, and permit the packets of VLAN 1002 and VLAN 1003 to pass through the port.

[Sysname] interface GigabitEthernet1/1/1

[Sysname-GigabitEthernet1/1/1] port link-type trunk

[Sysname-GigabitEthernet1/1/1] port trunk permit vlan 1002 1003

3 IGMP Snooping Configuration

IGMP snooping configurations mentioned in this chapter chiefly focus on the configurations for OLT devices. For details about the configurations for the ONU devices that are remotely performed on an OLT device, see Multicast Mode Configuration.

When configuring IGMP Snooping, go to the following sections for information you are interested in:

l IGMP Snooping Overview

l IGMP Snooping Configuration Task List

l Displaying and Maintaining IGMP Snooping

l IGMP Snooping Configuration Examples

l Troubleshooting IGMP Snooping Configuration

IGMP Snooping Overview

Internet Group Management Protocol Snooping (IGMP Snooping) is a multicast constraining mechanism that runs on Layer 2 devices to manage and control multicast groups.

Principle of IGMP Snooping

By analyzing received IGMP messages, an OLT device running IGMP Snooping or an ONU device configured with IGMP Snooping establishes mappings between ports and multicast MAC addresses and forwards multicast data based on these mappings.

As shown in Figure 3-1, when IGMP Snooping is not running on the OLT or ONU device, multicast packets are broadcast to all devices at Layer 2. When IGMP Snooping is running on the OLT or ONU device, multicast packets for known multicast groups are multicast to the receivers, rather than broadcast to all hosts, at Layer 2.

Figure 3-1 Before and after IGMP Snooping is enabled on the Layer 2 device

Basic Concepts in IGMP Snooping

IGMP Snooping related ports

As shown in Figure 3-2, Router A connects to the multicast source, IGMP Snooping runs on OLT switch, and Host B is receiver hosts (namely, multicast group members).

Figure 3-2 IGMP Snooping related ports

Ports involved in IGMP Snooping, as shown in Figure 3-2, are described as follows:

l Router port: For an OLT device, a router port is a port that leads the OLT towards a Layer 3 multicast device (DR or IGMP querier). In the figure, GigabitEthernet 1/1/1 of the OLT device is a router port. For an ONU device, a router port is a port that leads the ONU toward the OLT device. The OLT and ONU devices register all the local router ports in their router port lists.

l Member port: A member port is a port on an OLT or ONU device that leads the device towards multicast group members. In the figure, ONU 1/0/1:1 of the OLT device and UNI 2 of the ONU device are member ports. The OLT and ONU devices register all the local member ports in their IGMP Snooping forwarding table.

l Whenever mentioned in this document, a router port is a port on the OLT device that leads it to a Layer 3 multicast device and a port on the ONU device that leads it toward an OLT device, rather than a port on a router.

l An IGMP-snooping-enabled switch or an ONU device configured with IGMP snooping deems that all its ports on which IGMP general queries with the source IP address other than 0.0.0.0 or PIM hello messages are received are dynamic router ports.

Aging timers for dynamic ports in IGMP Snooping and related messages and actions

Table 3-1 Aging timers for dynamic ports in IGMP Snooping and related messages and actions

Timer	Description	Message before expiry	Action after expiry
Dynamic router port aging timer	For each dynamic router port, the OLT or the ONU sets a timer initialized to the dynamic router port aging time.	IGMP general query of which the source address is not 0.0.0.0 or PIM hello	The switch removes this port from its router port list.
Dynamic member port aging timer	When a port dynamically joins a multicast group, the OLT or the ONU sets a timer for the port, which is initialized to the dynamic member port aging time.	IGMP membership report	The switch removes this port from the IGMP Snooping forwarding table.

How IGMP Snooping Works

IGMP snooping is implemented in the same way on an OLT device and an ONU device. The following section shows how to implement IGMP snooping on an OLT device.

An OLT switch running IGMP Snooping performs different actions when it receives different IGMP messages, as follows:

When receiving a general query

The IGMP querier periodically sends IGMP general queries to all hosts and routers (224.0.0.1) on the local subnet to find out whether active multicast group members exist on the subnet.

Upon receiving an IGMP general query, the OLT switch forwards it through all ports in the VLAN except the receiving port and performs the following to the receiving port:

l If the receiving port is a dynamic router port existing in its router port list, the switch resets the aging timer of this dynamic router port.

l If the receiving port is not a dynamic router port existing in its router port list, the switch adds it into its router port list and sets an aging timer for this dynamic router port.

When receiving a membership report

A host sends an IGMP report to the IGMP querier in the following circumstances:

l Upon receiving an IGMP query, a multicast group member host responds with an IGMP report.

l When intended to join a multicast group, a host sends an IGMP report to the IGMP querier to announce that it is interested in the multicast information addressed to that group.

Upon receiving an IGMP report, the OLT switch forwards it through all the router ports in the VLAN, resolves the address of the reported multicast group, and performs the following:

l If no forwarding table entry exists for the reported group, the switch creates an entry, adds the port as a dynamic member port to the outgoing port list, and starts a member port aging timer for that port.

l If a forwarding table entry exists for the reported group, but the port is not included in the outgoing port list for that group, the switch adds the port as a dynamic member port to the outgoing port list, and starts an aging timer for that port.

l If a forwarding table entry exists for the reported group and the port is included in the outgoing port list, which means that this port is already a dynamic member port, the switch resets the aging timer for that port.

An OLT switch does not forward an IGMP report through a non-router port. The reason is as follows: Due to the IGMP report suppression mechanism, if the OLT switch forwards a report message through a member port, all the attached hosts listening to the reported multicast address will suppress their own reports upon receiving this report, and this will prevent the OLT switch from knowing whether the reported multicast group still has active members attached to that port.

When receiving a leave message

When an IGMPv1 host leaves a multicast group, the host does not send an IGMP leave message, so the OLT switch cannot know immediately that the host has left the multicast group. However, as the host stops sending IGMP reports as soon as it leaves a multicast group, the OLT switch deletes the forwarding entry for the dynamic member port corresponding to the host from the forwarding table when its aging timer expires.

When an IGMPv2 or IGMPv3 host leaves a multicast group, the host sends an IGMP leave message to the multicast router.

When the OLT switch receives an IGMP leave message on a dynamic member port, the OLT switch first checks whether a forwarding table entry for the group address in the message exists, and, if one exists, whether the outgoing port list contains the port.

l If the forwarding table entry does not exist or if the outgoing port list does not contain the port, the OLT switch discards the IGMP leave message instead of forwarding it to any port.

l If the forwarding table entry exists and the outgoing port list contains the port, the OLT switch forwards the leave message to all router ports in the native VLAN. Because the OLT switch does not know whether any other hosts attached to the port are still listening to that group address, the OLT switch does not immediately remove the port from the outgoing port list of the forwarding table entry for that group; instead, it resets the aging timer for the port.

Upon receiving the IGMP leave message from a host, the IGMP querier resolves the multicast group address in the message and sends an IGMP group-specific query to that multicast group through the port that received the leave message. Upon receiving the IGMP group-specific query, the OLT switch forwards it through all its router ports in the VLAN and all member ports for that multicast group, and performs the following to the port on which it received the IGMP leave message:

l If any IGMP report in response to the group-specific query is received on the port (suppose it is a dynamic member port) before its aging timer expires, this means that some host attached to the port is receiving or expecting to receive multicast data for that multicast group. The OLT switch resets the aging timer of the port.

l If no IGMP report in response to the group-specific query is received on the port before its aging timer expires, this means that no hosts attached to the port are still listening to that group address: the OLT switch removes the port from the outgoing port list of the forwarding table entry for that multicast group when the aging timer expires.

Protocols and Standards

IGMP Snooping is documented in:

l RFC 4541: Considerations for Internet Group Management Protocol (IGMP) and Multicast Listener Discovery (MLD) Snooping Switches

IGMP Snooping Configuration Task List

Complete these tasks to configure IGMP Snooping:

Task		Remarks
Configuring Basic Functions of IGMP Snooping	Enabling IGMP Snooping	Required
Configuring Basic Functions of IGMP Snooping	Configuring the Version of IGMP Snooping	Optional
Configuring IGMP Snooping Port Functions	Configuring Aging Timers for Dynamic Ports	Optional
	Configuring Simulated Joining	Optional
	Configuring Fast Leave Processing	Optional
Configuring IGMP Snooping Querier	Enabling IGMP Snooping Querier	Optional
	Configuring IGMP Queries and Responses	Optional
	Configuring Source IP Address of IGMP Queries	Optional
Configuring an IGMP Snooping Policy	Configuring a Multicast Group Filter	Optional
	Configuring Multicast Source Port Filtering	Optional
	Configuring the Function of Dropping Unknown Multicast Data	Optional
	Configuring IGMP Report Suppression	Optional
	Configuring Maximum Multicast Groups that Can Be Joined on a Port	Optional
	Configuring Multicast Group Replacement	Optional

l Configurations made in IGMP Snooping view are effective for all VLANs, while configurations made in VLAN view are effective only for ports belonging to the current VLAN. For a given VLAN, a configuration made in IGMP Snooping view is effective only if the same configuration is not made in VLAN view.

l Configurations made in IGMP Snooping view are effective for all ports; configurations made in Ethernet interface view are effective only for the current port; configurations made in Layer 2 aggregate interface view are effect only for the current interface; configurations made in port group view are effective only for all the ports in the current port group, configurations made in ONU port view are effective only for the current port. For a given port, a configuration made in IGMP Snooping view is effective only if the same configuration is not made in Ethernet interface view, Layer 2 aggregate interface view, port group view, or ONU port view.

l For IGMP Snooping, configurations made on a Layer 2 aggregate interface do not interfere with configurations made on its member ports, nor do they take part in aggregation calculations; configurations made on a member port of the aggregate group will not take effect until it leaves the aggregate group.

l Configurations mentioned in this section focus on the configurations for OLT devices; therefore, configurations made in ONU port view take effect for the current ONU port; configurations that are performed on an OLT device for the ONU device and are performed in ONU port view are effective for the ONU device.

Configuring Basic Functions of IGMP Snooping

Configuration Prerequisites

Before configuring the basic functions of IGMP Snooping, complete the following task:

l Configure the corresponding VLANs.

Before configuring the basic functions of IGMP Snooping, prepare the following data:

l Version of IGMP Snooping.

Enabling IGMP Snooping

Follow these steps to enable IGMP Snooping for an OLT device:

To do...	Use the command...	Remarks
Enter system view	system-view	—
Enable IGMP Snooping globally and enter IGMP-Snooping view	igmp-snooping	Required Disabled by default
Return to system view	quit	—
Enter VLAN view	vlan vlan-id	—
Enable IGMP Snooping in the VLAN	igmp-snooping enable	Required Disabled by default

l IGMP Snooping must be enabled globally for an OLT device before it can be enabled in a VLAN.

l When you enable IGMP Snooping in a specified VLAN, this function takes effect for the ports in this VLAN only.

Configuring the Version of IGMP Snooping

By configuring an IGMP Snooping version, you actually configure the version of IGMP messages that IGMP Snooping can process.

l IGMP Snooping version 2 can process IGMPv1 and IGMPv2 messages, but not IGMPv3 messages, which will be flooded in the VLAN.

l IGMP Snooping version 3 can process IGMPv1, IGMPv2 and IGMPv3 messages.

Follow these steps to configure the version of IGMP Snooping:

To do...	Use the command...	Remarks
Enter system view	system-view	—
Enter VLAN view	vlan vlan-id	—
Configure the version of IGMP Snooping	igmp-snooping version version-number	Optional Version 2 by default

If you switch IGMP Snooping from version 3 to version 2, the system will clear all IGMP Snooping forwarding entries from dynamic joins

Configuring IGMP Snooping Port Functions

Configuration Prerequisites

Before configuring IGMP Snooping port functions, complete the following tasks:

l Enable IGMP Snooping in the VLAN

l Configure the corresponding port groups.

l Create the corresponding ONU ports

Before configuring IGMP Snooping port functions, prepare the following data:

l Aging time of dynamic router ports,

l Aging time of dynamic member ports, and

l Multicast group and multicast source addresses

Configuring Aging Timers for Dynamic Ports

If the OLT switch receives no IGMP general queries or PIM hello messages on a dynamic router port, the switch removes the port from the router port list when the aging timer of the port expires.

If the OLT switch receives no IGMP reports for a multicast group on a dynamic member port, the switch removes the port from the outgoing port list of the forwarding table entry for that multicast group when the aging timer of the port for that group expires.

If multicast group memberships change frequently, you can set a relatively small value for the dynamic member port aging timer, and vice versa.

Configuring aging timers for dynamic ports globally

Follow these steps to globally configure aging timers for dynamic ports of the OLT device:

To do...	Use the command...	Remarks
Enter system view	system-view	—
Enter IGMP Snooping view	igmp-snooping	—
Configure dynamic router port aging time	router-aging-time interval	Optional 105 seconds by default
Configure dynamic member port aging time	host-aging-time interval	Optional 260 seconds by default

Configuring aging timers for dynamic ports in a VLAN

Follow these steps to configure aging timers for dynamic ports in a VLAN:

To do...	Use the command...	Remarks
Enter system view	system-view	—
Enter VLAN view	vlan vlan-id	—
Configure dynamic router port aging time	igmp-snooping router-aging-time interval	Optional 105 seconds by default
Configure dynamic member port aging time	igmp-snooping host-aging-time interval	Optional 260 seconds by default

Configuring Simulated Joining

Generally, a host running IGMP responds to IGMP queries from the IGMP querier. If a host fails to respond due to some reasons, the multicast router may deem that no member of this multicast group exists on the network segment, and therefore will remove the corresponding forwarding path.

To avoid this situation from happening, you can enable simulated joining on a port of the OLT switch, namely configure the port as a simulated member host for a multicast group. When receiving an IGMP query, the simulated host gives a response. Thus, the switch can continue receiving multicast data.

A simulated host acts like a real host, as follows:

l When a port is configured as a simulated member host, the OLT switch sends an unsolicited IGMP report through that port.

l After a port is configured as a simulated member host, the OLT switch responds to IGMP general queries by sending IGMP reports through that port.

l When the simulated joining function is disabled on a port, the OLT switch sends an IGMP leave message through that port.

Follow these steps to configure simulated joining:

To do...	Use the command...	Remarks
Enter system view	system-view	—
Enter Ethernet interface/Layer 2 aggregate interface/ONU port view or port group view	interface interface-type interface-number	Required Use either approach
	port-group manual port-group-name	Required Use either approach
Configure simulated (*, G) or (S, G) joining	igmp-snooping host-join group-address [ source-ip source-address ] vlan vlan-id	Required Disabled by default

l Each simulated host is equivalent to an independent host. For example, when receiving an IGMP query, the simulated host corresponding to each configuration responds respectively.

l A port configured as a simulated member host will age out like a dynamic member port.

Configuring Fast Leave Processing

The fast leave processing feature allows the OLT switch to process IGMP leave messages in a fast way. With the fast leave processing feature enabled, when receiving an IGMP leave message on a port, the switch immediately removes that port from the outgoing port list of the forwarding table entry for the indicated group. Then, when receiving IGMP group-specific queries for that multicast group, the OLT switch will not forward them to that port.

In VLANs where only one host is attached to each port, fast leave processing helps improve bandwidth and resource usage.

Configuring fast leave processing globally

Follow these steps to globally configure fast leave processing for the OLT device

To do...	Use the command...	Remarks
Enter system view	system-view	—
Enter IGMP Snooping view	igmp-snooping	—
Enable fast leave processing	fast-leave [ vlan vlan-list ]	Required Disabled by default

Configuring fast leave processing on a port or a group of ports

Follow these steps to configure fast leave processing on a port or a group of ports:

To do...	Use the command...	Remarks
Enter system view	system-view	—
Enter Ethernet interface/Layer 2 aggregate interface/ONU port view or port group view	interface interface-type interface-number	Required Use either approach
	port-group manual port-group-name	Required Use either approach
Enable fast leave processing	igmp-snooping fast-leave [ vlan vlan-list ]	Required Disabled by default

l The fast leave processing feature takes effect for multicast clients running IGMPv2 or IGMPv3.

l If fast leave processing is enabled on a port to which more than one host is attached, when one host leaves a multicast group, the other hosts attached to the port and interested in the same multicast group will fail to receive multicast data for that group.

Configuring IGMP Snooping Querier

Configuration Prerequisites

Before configuring IGMP Snooping querier, complete the following task:

l Enable IGMP Snooping in the VLAN.

l Create the corresponding ONU ports.

Before configuring IGMP Snooping querier, prepare the following data:

l IGMP general query interval,

l IGMP last-member query interval,

l Maximum response time to IGMP general queries,

l Source address of IGMP general queries, and

l Source address of IGMP group-specific queries.

Enabling IGMP Snooping Querier

In an IP multicast network running IGMP, a multicast router or Layer 3 multicast switch is responsible for sending IGMP general queries, so that all Layer 3 multicast devices can establish and maintain multicast forwarding entries, thus to forward multicast traffic correctly at the network layer. This router or Layer 3 switch is called an IGMP querier.

However, a Layer 2 multicast switch does not support IGMP, and therefore cannot send general queries by default. By enabling IGMP Snooping on a Layer 2 switch in a VLAN where multicast traffic needs to be Layer-2 switched only and no multicast routers are present, the Layer 2 switch will act as the IGMP Snooping querier to send IGMP queries, thus allowing multicast forwarding entries to be established and maintained at the data link layer.

Follow these steps to enable IGMP Snooping querier:

To do...	Use the command...	Remarks
Enter system view	system-view	—
Enter VLAN view	vlan vlan-id	—
Enable IGMP Snooping querier	igmp-snooping querier	Required Disabled by default

It is meaningless to configure an IGMP Snooping querier in a multicast network running IGMP. Although an IGMP Snooping querier does not take part in IGMP querier elections, it may affect IGMP querier elections because it sends IGMP general queries with a low source IP address.

Configuring IGMP Queries and Responses

You can tune the IGMP general query interval based on actual condition of the network.

Upon receiving an IGMP query (general query or group-specific query), a host starts a timer for each multicast group it has joined. This timer is initialized to a random value in the range of 0 to the maximum response time (the host obtains the value of the maximum response time from the Max Response Time field in the IGMP query it received). When the timer value comes down to 0, the host sends an IGMP report to the corresponding multicast group.

An appropriate setting of the maximum response time for IGMP queries allows hosts to respond to queries quickly and avoids bursts of IGMP traffic on the network caused by reports simultaneously sent by a large number of hosts when the corresponding timers expire simultaneously.

l For IGMP general queries, you can configure the maximum response time to fill their Max Response time field.

l For IGMP group-specific queries, you can configure the IGMP last-member query interval to fill their Max Response time field. Namely, for IGMP group-specific queries, the maximum response time equals to the IGMP last-member query interval.

Configuring IGMP queries and responses globally

Follow these steps to globally configure IGMP queries and responses for the OLT device:

To do...	Use the command...	Remarks
Enter system view	system-view	—
Enter IGMP Snooping view	igmp-snooping	—
Configure the maximum response time to IGMP general queries	max-response-time interval	Optional 10 seconds by default
Configure the IGMP last-member query interval	last-member-query-interval interval	Optional 1 second by default

Configuring IGMP queries and responses in a VLAN

Follow these steps to configure IGMP queries and responses in a VLAN:

To do...	Use the command...	Remarks
Enter system view	system-view	—
Enter VLAN view	vlan vlan-id	—
Configure IGMP general query interval	igmp-snooping query-interval interval	Optional 60 seconds by default
Configure the maximum response time to IGMP general queries	igmp-snooping max-response-time interval	Optional 10 seconds by default
Configure the IGMP last-member query interval	igmp-snooping last-member-query-interval interval	Optional 1 second by default

In the configuration, make sure that the IGMP general query interval is larger than the maximum response time for IGMP general queries. Otherwise, multicast group members may be deleted by mistake.

Configuring Source IP Address of IGMP Queries

Upon receiving an IGMP query whose source IP address is 0.0.0.0 on a port, the OLT switch does not enlist that port as a dynamic router port. This may prevent multicast forwarding entries from being correctly created at the data link layer and cause multicast traffic forwarding failure in the end. When an OLT switch acts as an IGMP-Snooping querier, to avoid the aforesaid problem, you are commended to configure a non-all-zero IP address as the source IP address of IGMP queries.

Follow these steps to configure source IP address of IGMP queries:

To do...	Use the command...	Remarks
Enter system view	system-view	—
Enter VLAN view	vlan vlan-id	—
Configure the source address of IGMP general queries	igmp-snooping general-query source-ip { current-interface \| ip-address }	Optional 0.0.0.0 by default
Configure the source IP address of IGMP group-specific queries	igmp-snooping special-query source-ip { current-interface \| ip-address }	Optional 0.0.0.0 by default

The source address of IGMP query messages may affect IGMP querier selection within the segment.

Configuring an IGMP Snooping Policy

Configuration Prerequisites

Before configuring an IGMP Snooping policy, complete the following task:

l Enable IGMP Snooping in the VLAN

l Configure the corresponding port groups

l Create the corresponding ONU ports

Before configuring an IGMP Snooping policy, prepare the following data:

l ACL rule for multicast group filtering

l The maximum number of multicast groups that can pass the ports

Configuring a Multicast Group Filter

On an IGMP Snooping–enabled OLT switch, the configuration of a multicast group allows the service provider to define restrictions on multicast programs available to different users.

In an actual application, when a user requests a multicast program, the user’s host initiates an IGMP report. Upon receiving this report message, the OLT switch checks the report against the configured ACL rule. If the port on which the report was received can join this multicast group, the OLT switch adds an entry for this port in the IGMP Snooping forwarding table; otherwise the OLT switch drops this report message. Any multicast data that has failed the ACL check will not be sent to this port. In this way, the service provider can control the VOD programs provided for multicast users.

Configuring a multicast group filter globally

Follow these steps to globally configure a multicast group filter for the OLT device::

To do...	Use the command...	Remarks
Enter system view	system-view	—
Enter IGMP Snooping view	igmp-snooping	—
Configure a multicast group filter	group-policy acl-number [ vlan vlan-list ]	Required No group filter is configured by default.

Configuring a multicast group filter on a port or a group of ports

Follow these steps to configure a multicast group filter on a port or a group of ports:

To do...	Use the command...	Remarks
Enter system view	system-view	—
Enter Ethernet interface/Layer 2 aggregate interface/ONU port view or port group view	interface interface-type interface-number	Required Use either approach
	port-group manual port-group-name	Required Use either approach
Configure a multicast group filter	igmp-snooping group-policy acl-number [ vlan vlan-list ]	Required No group filter is configured by default.

Configuring Multicast Source Port Filtering

With the multicast source port filtering feature enabled on a port, the port can be connected with multicast receivers only rather than with multicast sources, because the port will block all multicast data packets while it permits multicast protocol packets to pass.

If this feature is disabled on a port, the port can be connected with both multicast sources and multicast receivers.

Configuring multicast source port filtering globally

Follow these steps to globally configure multicast source port filtering for the OLT device:

To do...	Use the command...	Remarks
Enter system view	system-view	—
Enter IGMP Snooping view	igmp-snooping	—
Enable multicast source port filtering	source-deny port interface-list	Required Disabled by default

Configuring multicast source port filtering on a port or a group of ports

Follow these steps to configure multicast source port filtering on a port or a group of ports:

To do...	Use the command...	Remarks
Enter system view	system-view	—
Enter Ethernet interface/OLT port view or port group view	interface interface-type interface-number	Required Use either approach
Enter Ethernet interface/OLT port view or port group view	port-group manual port-group-name	Required Use either approach
Enable multicast source port filtering	igmp-snooping source-deny	Required Disabled by default

Configuring the Function of Dropping Unknown Multicast Data

Unknown multicast data refers to multicast data for which no entries exist in the IGMP Snooping forwarding table. When the switch receives such multicast traffic:

l With the function of dropping unknown multicast data enabled, the OLT switch drops all the unknown multicast data received.

l With the function of dropping unknown multicast data disabled, the OLT switch floods unknown multicast data in the VLAN which the unknown multicast data belongs to.

Follow these steps to configure the function of dropping unknown multicast data in a VLAN:

To do...	Use the command...	Remarks
Enter system view	system-view	—
Enter VLAN view	vlan vlan-id	—
Enable the function of dropping unknown multicast data	igmp-snooping drop-unknown	Required Disabled by default

Configuring IGMP Report Suppression

When an OLT switch receives an IGMP report from a multicast group member, the switch forwards the message to the Layer 3 device directly connected with it. Thus, when multiple members of a multicast group are attached to the switch, the Layer 3 device directly connected with it will receive duplicate IGMP reports from these members.

With the IGMP report suppression function enabled, within each query cycle, the OLT switch forwards only the first IGMP report per multicast group to the Layer 3 device and will not forward the subsequent IGMP reports from the same multicast group to the Layer 3 device. This helps reduce the number of packets being transmitted over the network.

Follow these steps to configure IGMP report suppression for the OLT device:

To do...	Use the command...	Remarks
Enter system view	system-view	—
Enter IGMP Snooping view	igmp-snooping	—
Enable IGMP report suppression	report-aggregation	Optional Enabled by default

Configuring Maximum Multicast Groups that Can Be Joined on a Port

By configuring the maximum number of multicast groups that can be joined on a port, you can limit the number of multicast programs on-demand available to users, thus to regulate traffic on the port.

Follow these steps to configure the maximum number of multicast groups allowed on a port or ports:

To do...	Use the command...	Remarks
Enter system view	system-view	—
Enter Ethernet interface/Layer 2 aggregate interface/ONU port view or port group view	interface interface-type interface-number	Required Use either approach
	port-group manual port-group-name	Required Use either approach
Configure the maximum number of multicast groups allowed on the port(s)	igmp-snooping group-limit limit [ vlan vlan-list ]	Optional 1000 by default.

l When the number of multicast groups a port has joined reaches the maximum number configured, the system deletes all the forwarding entries persistent to that port from the IGMP Snooping forwarding table, and the hosts on this port need to join the multicast groups again.

l If you have configured simulated joins on a port, however, when the number of multicast groups on the port exceeds the configured threshold, the system deletes all the forwarding entries persistent to that port from the IGMP Snooping forwarding table and applies the static or simulated joins again, until the number of multicast groups joined by the port comes back within the configured threshold.

Configuring Multicast Group Replacement

For some special reasons, the number of multicast groups that can be joined on the current OLT switch or port may exceed the number configured for the OLT switch or the port. In addition, in some specific applications, a multicast group newly joined on the switch needs to replace an existing multicast group automatically. A typical example is “channel switching”, namely, by joining a new multicast group, a user automatically switches from the current multicast group to the new one.

To address such situations, you can enable the multicast group replacement function on the switch or certain ports. When the number of multicast groups joined on the switch or a port has joined reaches the limit:

l If the multicast group replacement feature is enabled, the newly joined multicast group automatically replaces an existing multicast group with the lowest address.

l If the multicast group replacement feature is not enabled, new IGMP reports will be automatically discarded.

Configuring multicast group replacement globally

Follow these steps to globally configure multicast group replacement for the OLT device:

To do...	Use the command...	Remarks
Enter system view	system-view	—
Enter IGMP Snooping view	igmp-snooping	—
Enable multicast group replacement	overflow-replace [ vlan vlan-list ]	Required Disabled by default

Configuring multicast group replacement on a port or a group of ports

Follow these steps to configure multicast group replacement on a port or a group of ports:

To do...	Use the command...	Remarks
Enter system view	system-view	—
Enter Ethernet interface/Layer 2 aggregate interface/ONU port view or port group view	interface interface-type interface-number	Required Use either approach
	port-group manual port-group-name	Required Use either approach
Enable multicast group replacement	igmp-snooping overflow-replace [ vlan vlan-list ]	Required Disabled by default

Be sure to configure the maximum number of multicast groups allowed on a port (refer to Configuring Maximum Multicast Groups that Can Be Joined on a Port) before enabling multicast group replacement. Otherwise, the multicast group replacement functionality will not take effect.

Displaying and Maintaining IGMP Snooping

To do...	Use the command...	Remarks
View IGMP Snooping multicast group information	display igmp-snooping group [ vlan vlan-id ] [ verbose ]	Available in any view
View the statistics information of IGMP messages learned by IGMP Snooping	display igmp-snooping statistics	Available in any view
Clear IGMP Snooping multicast group information	reset igmp-snooping group { group-address \| all } [ vlan vlan-id ]	Available in user view
Clear the statistics information of all kinds of IGMP messages learned by IGMP Snooping	reset igmp-snooping statistics	Available in user view

The reset igmp-snooping group command cannot clear the IGMP Snooping multicast group information for static joins.

IGMP Snooping Configuration Examples

Configuring Group Policy and Simulated Joining

Network requirements

l As shown in Figure 3-3, Router A connects to the multicast source through GigabitEthernet2/0/2 and to OLT through GigabitEthernet2/0/1.

l IGMPv2 is required on Router A, IGMP Snooping version 2 is required on OLT, and Router A will act as the IGMP querier on the subnet.

l OLT connects to Router A through GigabitEthernet 1/1/1 and to POS with ONU attached through OLT 1/0/1. ONU is bound to ONU 1/0/1:1. Host A, Host B, and Host C are attached to ONU through UNI 1, UNI 2, and UNI 3 respectively.

l It is required that the receivers, Host A and Host B, attached to ONU can receive multicast traffic addressed to multicast group 224.1.1.1 only.

l It is required that multicast data for group 224.1.1.1 can be forwarded through ONU 1/0/1:1 on OLT even if Host A and Host B accidentally, temporarily stop receiving multicast data.

Network diagram

Figure 3-3 Network diagram for group policy simulated joining configuration

Configuration procedure

Prior configurations for the OLT and ONU devices are required to ensure that ONU can succeed in registering with OLT. For details, see EPON-OLT Configuration.

1) Configure IP addresses

Configure an IP address and subnet mask for each interface as per Figure 3-3. The detailed configuration steps are omitted.

2) Configure Router A

# Enable IP multicast routing, enable PIM-DM on each interface, and enable IGMP on GigabitEthernet 2/0/1.

<RouterA> system-view

[RouterA] multicast routing-enable

[RouterA] interface gigabitEthernet2/0/1

[RouterA-GigabitEthernet2/0/1] igmp enable

[RouterA-GigabitEthernet2/0/1] pim dm

[RouterA-GigabitEthernet2/0/1] quit

[RouterA] interface gigabitEthernet2/0/2

[RouterA-GigabitEthernet2/0/2] pim dm

[RouterA-GigabitEthernet2/0/2] quit

3) Configure OLT

# Map the multicast addresses to multicast VLANs..

<Sysname> system-view

[Sysname] ftth

[Sysname-ftth] multicast vlan-id 1002 dest-ip 224.1.1.1 to 224.1.1.255

[Sysname-ftth] quit

# Enable IGMP Snooping globally

[Sysname] igmp-snooping

[Sysname-igmp-snooping] quit

# Create VLAN 1002, and enable IGMP Snooping and the function of dropping unknown multicast traffic in the VLAN.

[Sysname] vlan 1002

[Sysname-vlan1002] igmp-snooping enable

[Sysname-vlan1002] igmp-snooping drop-unknown

[Sysname-vlan1002] quit

# Configure the multicast mode of the ONU as IGMP snooping.

[Sysname] interface onu 1/0/1:1

[Sysname-Onu1/0/1:1] multicast-mode igmp-snooping

# Assign UNI 1 and UNI 2 to multicast VLAN 1002, and configure the ONU as a Trunk port (to allow the packets of all the VLANs to pass through the port).

[Sysname-Onu1/0/1:1] port link-type trunk

[Sysname-Onu1/0/1:1] uni 1 multicast vlan 1002

[Sysname-Onu1/0/1:1] uni 2 multicast vlan 1002

# Configure the link type of OLT 1/0/1 as hybrid, allow the packets of VLAN 1002 to pass through OLT 1/0/1, and add tags to the VLAN 1002 packets sent by OLT 1/0/1.

[Sysname] interface olt 1/0/1

[Sysname-Olt1/0/1] port link-type hybrid

[Sysname-Olt1/0/1] port hybrid vlan 1002 tagged

# Configure GigabitEthernet1/1/1 as a Trunk port, and permit the packets of VLAN 1002 to pass.

[Sysname] interface GigabitEthernet1/1/1

[Sysname-GigabitEthernet1/1/1] port link-type trunk

[Sysname-GigabitEthernet1/1/1] port trunk permit vlan 1002

# Configure a multicast group filter for the OLT so that the hosts in VLAN 1002 can join only the multicast group 224.1.1.1.

[Sysname] acl number 2001

[Sysname -acl-basic-2001] rule permit source 224.1.1.1 0

[Sysname -acl-basic-2001] quit

[Sysname] igmp-snooping

[Sysname -igmp-snooping] group-policy 2001 vlan 1002

[Sysname -igmp-snooping] quit

# Configure Onu 1/0/1:1 as simulated hosts for multicast group 224.1.1.1.

[Sysname] interface onu1/0/1:1

[Sysname -Onu1/0/1:1] igmp-snooping host-join 224.1.1.1 vlan 1002

[Sysname -Onu1/0/1:1] quit

4) Verify the configuration

# View the detailed IGMP Snooping multicast groups information in VLAN 1002 on OLT.

[Sysname] display igmp-snooping group vlan 1002 verbose

Total 1 IP Group(s).

Total 1 IP Source(s).

Total 1 MAC Group(s).

Port flags: D-Dynamic port, S-Static port, C-Copy port

Subvlan flags: R-Real VLAN, C-Copy VLAN

Vlan(id):1002.

Total 1 IP Group(s).

Total 1 IP Source(s).

Total 1 MAC Group(s).

Router port(s):total 1 port.

GE1/1/1 (D) ( 00:01:30 )

IP group(s):the following ip group(s) match to one mac group.

IP group address:224.1.1.1

(0.0.0.0, 224.1.1.1):

Attribute: Host Port

Host port(s):total 1 port.

Onu1/0/1:1 (D) ( 00:03:23 )

MAC group(s):

MAC group address:0100-5e01-0101

Host port(s):total 1 port.

Onu1/0/1:1

As shown above, ONU1/0/1:1 of OLT has joined multicast group 224.1.1.1.

IGMP Snooping Querier Configuration

Network requirements

l As shown in Figure 3-4, in a Layer 2–only network environment, multicast sources Source 1 send multicast data to multicast groups 224.1.1.1, Host A is receiver of multicast group 224.1.1.1.

l The receiver is running IGMPv2, and all the switches (include the OLT and the Switch A) need to run IGMP Snooping version 2. The OLT, which is close to the multicast sources, is chosen as the IGMP-Snooping querier.

l To prevent flooding of unknown multicast traffic within the VLAN, it is required to configure all the switches (include the OLT and the Switch A) to drop unknown multicast data packets.

l Because the OLT and the Switch A do not enlist a port that has heard an IGMP query with a source IP address of 0.0.0.0 (default) as a dynamic router port, configure a non-all-zero IP address as the source IP address of IGMP queries to ensure normal creation of Layer 2 multicast forwarding entries.

Network diagram

Figure 3-4 Network diagram for IGMP Snooping querier configuration

Configuration procedure

Prior configurations for the OLT and ONU devices are required to ensure that ONU can succeed in registering with OLT. For details, see EPON-OLT Configuration.

1) Configure OLT

# Map the multicast addresses to multicast VLANs..

<Sysname> system-view

[Sysname] ftth

[Sysname-ftth] multicast vlan-id 1002 dest-ip 224.1.1.1 to 224.1.1.255

[Sysname-ftth] quit

# Enable IGMP Snooping globally

[Sysname] igmp-snooping

[Sysname-igmp-snooping] quit

# Create VLAN 1002, and enable IGMP Snooping and the function of dropping unknown multicast traffic in the VLAN.

[Sysname] vlan 1002

[Sysname-vlan1002] igmp-snooping enable

[Sysname-vlan1002] igmp-snooping drop-unknown

[Sysname-vlan1002] quit

# Configure the multicast mode of the ONU as IGMP snooping.

[Sysname] interface onu 1/0/1:1

[Sysname-Onu1/0/1:1] multicast-mode igmp-snooping

# Assign UNI 1 to multicast VLAN 1002, and configure the ONU as a Trunk port (to allow the packets of all the VLANs to pass through the port).

[Sysname-Onu1/0/1:1] port link-type trunk

[Sysname-Onu1/0/1:1] uni 1 multicast vlan 1002

# Configure the link type of OLT 1/0/1 as hybrid, allow the packets of VLAN 1002 to pass through OLT 1/0/1, and add tags to the VLAN 1002 packets sent by OLT 1/0/1.

[Sysname] interface olt 1/0/1

[Sysname-Olt1/0/1] port link-type hybrid

[Sysname-Olt1/0/1] port hybrid vlan 1002 tagged

# Configure GigabitEthernet1/1/1 as a Trunk port, and permit the packets of VLAN 1002 to pass.

[Sysname] interface GigabitEthernet1/1/1

[Sysname-GigabitEthernet1/1/1] port link-type trunk

[Sysname-GigabitEthernet1/1/1] port trunk permit vlan 1002

# Enable the IGMP-Snooping querier function in VLAN 100

[Sysname -vlan100] igmp-snooping querier

# Set the source IP address of IGMP general queries and group-specific queries to 192.168.1.1 in VLAN 1002.

[Sysname -vlan1002] igmp-snooping general-query source-ip 192.168.1.1

[Sysname -vlan1002] igmp-snooping special-query source-ip 192.168.1.1

[Sysname -vlan1002] quit

2) Configure Switch A

# Enable IGMP Snooping globally.

< Sysname > system-view

[Sysname] igmp-snooping

[Sysname -igmp-snooping] quit

# Create VLAN 1002, and assign GigabitEthernet2/0/1 to GigabitEthernet2/0/3 to the VLAN.

[Sysname] vlan 1002

[Sysname -vlan1002] port gigabitEthernet2/0/1 to gigabitEthernet2/0/3

# Enable IGMP Snooping and the function of dropping unknown multicast traffic in VLAN 1002.

[Sysname -vlan1002] igmp-snooping enable

[Sysname -vlan1002] igmp-snooping drop-unknown

[Sysname -vlan1002] quit

3) Verify the configuration

After the IGMP Snooping querier starts to work, Switch A can receive IGMP general queries. By using the display igmp-snooping statistics command, you can view the statistics information about the IGMP messages received. For example:

# View the IGMP message statistics on Switch A.

[Sysname] display igmp-snooping statistics

Received IGMP general queries:3.

Received IGMPv1 reports:0.

Received IGMPv2 reports:12.

Received IGMP leaves:0.

Received IGMPv2 specific queries:0.

Sent IGMPv2 specific queries:0.

Received IGMPv3 reports:0.

Received IGMPv3 reports with right and wrong records:0.

Received IGMPv3 specific queries:0.

Received IGMPv3 specific sg queries:0.

Sent IGMPv3 specific queries:0.

Sent IGMPv3 specific sg queries:0.

Received error IGMP messages:0.

Troubleshooting IGMP Snooping Configuration

Switch Fails in Layer 2 Multicast Forwarding

Symptom

An OLT switch fails to implement Layer 2 multicast forwarding.

Analysis

IGMP Snooping is not enabled.

Solution

l Enter the display current-configuration command to view the running status of IGMP Snooping.

l If IGMP Snooping is not enabled, use the igmp-snooping command to enable IGMP Snooping globally, and then use igmp-snooping enable command to enable IGMP Snooping in VLAN view.

l If IGMP Snooping is disabled only for the corresponding VLAN, just use the igmp-snooping enable command in VLAN view to enable IGMP Snooping in the corresponding VLAN.

Configured Multicast Group Policy Fails to Take Effect

Symptom

Although a multicast group policy has been configured to allow hosts to join specific multicast groups, the hosts can still receive multicast data addressed to other multicast groups.

Analysis

l The ACL rule is incorrectly configured.

l The multicast group policy is not correctly applied.

l The function of dropping unknown multicast data is not enabled, so unknown multicast data is flooded.

Solution

l Use the display acl command to check the configured ACL rule. Make sure that the ACL rule conforms to the multicast group policy to be implemented.

l Use the display this command in IGMP Snooping view or in the corresponding interface view to check whether the correct multicast group policy has been applied. If not, use the group-policy or igmp-snooping group-policy command to apply the correct multicast group policy.

l Use the display current-configuration command to check whether the function of dropping unknown multicast data is enabled. If not, use the igmp-snooping drop-unknown command to enable the function of dropping unknown multicast data.

4 Multicast VLAN Configuration

When configuring multicast VLAN, go to these sections for information you are interested in:

l Introduction to Multicast VLAN

l Multicast VLAN Configuration Task List

l Configuring Sub-VLAN-Based Multicast VLAN

l Configuring Port-Based Multicast VLAN

l Displaying and Maintaining Multicast VLAN

Introduction to Multicast VLAN

As shown in Figure 4-1, in the traditional multicast programs-on-demand mode, when hosts, Host A, Host B and Host C, belonging to different VLANs require multicast programs on demand service, the Layer 3 device, Router A, needs to forward a separate copy of the multicast traffic in each user VLAN to the Layer 2 device, OLT switch. This results in not only waste of network bandwidth but also extra burden on the Layer 3 device.

Figure 4-1 Multicast transmission without multicast VLAN

The multicast VLAN feature configured on the Layer 2 device is the solution to this issue. With the multicast VLAN feature, the Layer 3 device needs to replicate the multicast traffic only in the multicast VLAN instead of making a separate copy of the multicast traffic in each user VLAN. This saves the network bandwidth and lessens the burden of the Layer 3 device.

The multicast VLAN feature can be implemented in two approaches, as described below:

Sub-VLAN-based multicast VLAN

As shown in Figure 4-2, Host A, Host B and Host C are in three different user VLANs. On OLT switch, configure VLAN 10 as a multicast VLAN, configure all the user VLANs as sub-VLANs of this multicast VLAN, and enable IGMP Snooping in the multicast VLAN.

Figure 4-2 Sub-VLAN-based multicast VLAN

After the configuration, IGMP Snooping manages router ports in the multicast VLAN and member ports in the sub-VLANs. When forwarding multicast data to Switch A, Router A needs to send only one copy of multicast traffic to OLT switch in the multicast VLAN, and OLT switch distributes the traffic to the multicast VLAN’s sub-VLANs that contain receivers.

Port-based multicast VLAN

To implement port-based multicast VLAN, configure a multicast VLAN on the switch, assign all the ports to the multicast VLAN, and enable IGMP snooping in the multicast VLAN and all user VLANs. After the configuration, the router port and member ports are uniformly maintained in the multicast VLAN and only one copy of the multicast traffic needs to be forwarded to the switch in the multicast VLAN. The switch then distributes the traffic to all the member ports in the multicast VLAN.

Multicast VLAN Configuration Task List

Complete the following tasks to configure multicast VLAN:

Task		Remarks
Configuring Sub-VLAN-Based Multicast VLAN		Required Use either approach.
Configuring Port-Based Multicast VLAN	Configuring User Port Attributes
Configuring Port-Based Multicast VLAN	Configuring Multicast VLAN Ports

If you have configured both sub-VLAN-based multicast VLAN and port-based multicast VLAN on a device, the port-based multicast VLAN configuration is given preference.

Configuring Sub-VLAN-Based Multicast VLAN

Configuration Prerequisites

Before configuring sub-VLAN-based multicast VLAN, complete the following tasks:

l Create VLANs as required

l Enable IGMP Snooping in the VLAN to be configured as a multicast VLAN

Configuring Sub-VLAN-Based Multicast VLAN

In this approach, you need to configure a VLAN as a multicast VLAN, and then configure user VLANs as sub-VLANs of the multicast VLAN.

Follow these steps to configure sub-VLAN-based multicast VLAN:

To do…	Use the command…	Remarks
Enter system view	system-view	—
Configure the specified VLAN as a multicast VLAN and enter multicast VLAN view	multicast-vlan vlan-id	Required Not a multicast VLAN by default
Configure the specified VLAN(s) as sub-VLAN(s) of the multicast VLAN	subvlan vlan-list	Required By default, a multicast VLAN has no sub-VLANs.

l The VLAN to be configured as a multicast VLAN must exist.

l The VLANs to be configured as sub-VLANs of the multicast VLAN must exist and must not be sub-VLANs of another multicast VLAN.

l The total number of sub-VLANs of a multicast VLAN must not exceed the maximum number the system can support. S3600 series EPON OLT switch supports one multicast VLAN, and supports up to 127 sub-VLANs for the multicast VLAN.

Configuring Port-Based Multicast VLAN

When configuring port-based multicast VLAN, you need to configure the attributes of each user port and then assign the ports to the multicast VLAN.

l A user port can be configured as a multicast VLAN port only if it is of the Ethernet, or Layer 2 aggregate interface type.

l Configurations made in Ethernet interface view is effective only for the current port; configurations made in Layer 2 aggregate interface view are effective only for the current interface

Configuration Prerequisites

Before configuring port-based multicast VLAN, complete the following tasks:

l Create VLANs as required

l Enable IGMP Snooping in the VLAN to be configured as a multicast VLAN

l Enable IGMP Snooping in all the user VLANs

Configuring User Port Attributes

Configure the user ports as hybrid ports that permit packets of the specified user VLAN to pass, and configure the user VLAN to which the user ports belong as the default VLAN.

Configure the user ports to permit packets of the multicast VLAN to pass and untag the packets. Thus, upon receiving multicast packets tagged with the multicast VLAN ID from the upstream device, the Layer 2 device untags the multicast packets and forwards them to its downstream device.

Follow these steps to configure user port attributes:

To do...	Use the command...	Remarks
Enter system view	system-view	—
Enter interface view or port group view	interface interface-type interface-number	Required Use either command
Enter interface view or port group view	port-group { manual port-group-name \| aggregation agg-id }	Required Use either command
Configure the user port link type as hybrid	port link-type hybrid	Required Access by default
Specify the user VLAN that comprises the current user port(s) as the default VLAN	port hybrid pvid vlan vlan-id	Required VLAN 1 by default
Configure the current user port(s) to permit packets of the specified multicast VLAN(s) to pass and untag the packets	port hybrid vlan vlan-id-list untagged	Required By default, a hybrid port permits only packets of VLAN 1 to pass.

For details about the port link-type, port hybrid pvid vlan, and port hybrid vlan commands, refer to VLAN Commands.

Configuring Multicast VLAN Ports

In this approach, you need to configure a VLAN as a multicast VLAN and then assign user ports to this multicast VLAN by either adding the user ports in the multicast VLAN or specifying the multicast VLAN on the user ports. These two configuration methods give the same result.

Configuring multicast VLAN ports in multicast VLAN view

Follow these steps to configure multicast VLAN ports in multicast VLAN view:

To do...	Use the command...	Remarks
Enter system view	system-view	—
Configure the specified VLAN as a multicast VLAN and enter multicast VLAN view	multicast-vlan vlan-id	Required Not a multicast VLAN by default
Assign ports to the multicast VLAN	port interface-list	Required By default, a multicast VLAN has no ports.

Configuring multicast VLAN ports in interface view or port group view

Follow these steps to configure multicast VLAN ports in interface view or port group view:

To do…	Use this command…	Remarks
Enter system view	system-view	—
Configure the specified VLAN as a multicast VLAN and enter multicast VLAN view	multicast-vlan vlan-id	Required Not a multicast VLAN by default.
Return to system view	quit	—
Enter interface view or port group view	interface interface-type interface-number	Required Use either command.
Enter interface view or port group view	port-group manual port-group-name	Required Use either command.
Configure the current port(s) as port(s) of the multicast VLAN	port multicast-vlan vlan-id	Required By default, a user port does not belong to any multicast VLAN.

l You cannot configure multicast VLAN on a device with multicast routing enabled.

l The VLAN to be configured as a multicast VLAN must exist.

l A port can belong to only one multicast VLAN.

Displaying and Maintaining Multicast VLAN

To do…	Use the command…	Remarks
Display information about a multicast VLAN	display multicast-vlan [ vlan-id ]	Available in any view

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H3C S3600 Series EPON OLT Switches Operation Manual-Release 3103-6W100

Table of Content

21-Mulitcast Configuration

Unicast

Multicast

Common Notations in Multicast

Advantages of multicast

Applications of multicast

ASM model

SFM model

SSM model

Ethernet multicast MAC addresses

Multicast Protocols

Layer 3 multicast protocols

Layer 2 multicast protocols

Multicast Packet Forwarding Mechanism

Multicast Modes of ONU Devices

Overview

IGMP Snooping Mode

Multicast control mode

Configuring the IGMP Snooping Mode for the ONU Device

Displaying and Maintaining the Multicast Modes for ONU Devices

Network requirements

Network diagram

Configuration procedure

Network requirements

Network diagram

Configuration procedure

IGMP Snooping Overview

IGMP Snooping related ports

Aging timers for dynamic ports in IGMP Snooping and related messages and actions

When receiving a general query

When receiving a membership report

When receiving a leave message

Configuring Basic Functions of IGMP Snooping

Enabling IGMP Snooping

Configuring the Version of IGMP Snooping

Configuring IGMP Snooping Port Functions

Configuring Aging Timers for Dynamic Ports

Configuring aging timers for dynamic ports globally

Configuring aging timers for dynamic ports in a VLAN

Configuring Simulated Joining

Configuring Fast Leave Processing

Configuring fast leave processing globally

Configuring fast leave processing on a port or a group of ports

Configuring IGMP Snooping Querier

Enabling IGMP Snooping Querier

Configuring IGMP Queries and Responses

Configuring IGMP queries and responses globally

Configuring IGMP queries and responses in a VLAN

Configuring Source IP Address of IGMP Queries

Configuring an IGMP Snooping Policy

Configuring a Multicast Group Filter

Configuring a multicast group filter globally

Configuring a multicast group filter on a port or a group of ports

Configuring Multicast Source Port Filtering

Configuring multicast source port filtering globally

Configuring multicast source port filtering on a port or a group of ports

Configuring the Function of Dropping Unknown Multicast Data

Configuring Multicast Group Replacement

Configuring multicast group replacement globally

Configuring multicast group replacement on a port or a group of ports

Displaying and Maintaining IGMP Snooping

IGMP Snooping Configuration Examples

Network requirements

Network diagram

Configuration procedure

Network requirements

Network diagram

Configuration procedure

Symptom

Analysis

Solution

Symptom

Analysis

Solution

Sub-VLAN-based multicast VLAN

Port-based multicast VLAN

Configuring multicast VLAN ports in multicast VLAN view

Configuring multicast VLAN ports in interface view or port group view