· MVPN—An MVPN logically defines the transmission boundary of the multicast traffic of a VPN over the public network. It also physically identifies all the PEs that support that VPN instance on the public network. Different VPN instances correspond to different MVPNs. All PEs in an MVPN are MVPN peers.

· Inclusive tunnel—Transmits all multicast packets (including multicast protocol packets and multicast data packets of all multicast groups) for an MVPN. Only one inclusive tunnel can be established between two PEs in the MVPN. A PE encapsulates multicast data packets and PIM BSMs of an MVPN into public network multicast data packets and sends them over the public network through the inclusive tunnel.

· Selective tunnel—Transmits multicast packets of one or more multicast groups for an MVPN. Multiple selective tunnels can be established between two PEs in the MVPN.

mLDP-based MVPN operation

The operation of mLDP-based MVPN is similar to that of RSVP-TE-based MVPN. They differ in the direction in which the public network P2MP tunnel is created.

· RSVP-TE-based MVPN—Starting from the ingress PE, the upstream devices use RSVP to establish RSVP-TE P2MP tunnels with downstream devices. In this mode, the ingress PE needs to know the IP address of the egress PE.

· mLDP-based MVPN—Starting from the egress PE, the downstream devices use LDP to establish mLDP P2MP tunnels with downstream devices. In this mode, the egress PE needs to the IP address of the ingress PE.

For more information about the RSVP-TE-based MVPN operation, see "Configuring RSVP-TE-based MVPN."

Inclusive tunnel establishment

As shown in Figure 1, the private network runs PIM, and the public network uses MPLS backbone. The inclusive tunnels are established as follows:

1. PE 1, PE 2, and PE 3 mutually establish IBGP neighbor relationship and exchange routing information.

2. PE 1 (the source of the tunnel) advertises the inclusive tunnel information to PE 2 and PE 3.

3. PE 2 and PE 3 each uses LDP to establish an inclusive mLDP tunnel with PE 1. The inclusive tunnel on the public network does not rely on PIM running on the private network.

Figure 1 Establishment of the inclusive tunnel

Selective tunnel establishment and tunnel switchover

mLDP-based MVPN supports switchover from the inclusive tunnel to selective tunnels to off-load traffic for specific (S, G) entries from the inclusive tunnel. An MVPN can have multiple selective tunnels.

As shown in Figure 2, the process of selective tunnel creation and the tunnel switchover is as follows:

1. Upon receiving a multicast packet for the (S, G) entry that meets the tunnel switchover criterion, the multicast source-side PE 1 sends an S-PMSI A-D route to PE 2 and PE 3.

2. PE 2 does not respond to the route because it has no receivers of the (S,G) entry attached.

3. PE 3 which has a receiver attached uses LDP to establish a selective tunnel with PE 1.

4. Subsequent multicast packets for the (S,G) entry are transmitted over the selective tunnel instead of the inclusive tunnel on the public network.

Figure 2 Selective tunnel establishment and tunnel switchover

Inter-AS mLDP-based MVPN

In an inter-AS VPN networking scenario, VPN sites are located in multiple ASs. These sites must be interconnected. Inter-AS VPN provides the following solutions:

· VRF-to-VRF connections between ASBRs—This solution is also called inter-AS option A.

· EBGP redistribution of labeled VPN-IPv4 routes between ASBRs—ASBRs advertise VPN-IPv4 routes to each other through MP-EBGP. This solution is also called inter-AS option B.

· Multihop EBGP redistribution of labeled VPN-IPv4 routes between PE devices—PEs advertise VPN-IPv4 routes to each other through MP-EBGP. This solution is also called inter-AS option C.

For more information about the three inter-AS VPN solutions, see MPLS L3VPN configuration in MPLS Configuration Guide.

Inter-AS option A mLDP-based MVPN

As shown in Figure 3:

· A VPN instance spans AS 100 and AS 200.

· PE 3 and PE 4 are ASBRs for AS 100 and AS 200, respectively.

· PE 3 and PE 4 are interconnected through their respective VPN instance and treat each other as a CE.

Figure 3 Inter-AS option A mLDP-based MVPN

To implement inter-AS option A mLDP-based MVPN, a separate MVPN must be created in each AS. Multicast data of the VPN instance is transmitted across the ASs through the separate MVPNs in each AS.

Multicast packets of the VPN instance are delivered as follows:

1. CE 1 forwards a multicast packet of VPN instance 1 to PE 1.

2. PE 1 encapsulates the multicast packet into an MPLS packet and forwards it to PE 3 through mLDP tunnel 1.

3. PE 3 considers PE 4 as a CE of MVPN 1, so PE 3 decapsulates the MPLS packet and forwards the multicast packet to PE 4.

4. PE 4 considers PE 2 as a CE of MVPN 2, so PE 4 encapsulates the multicast packet into an MPLS packet and then forwards the packet to PE 2 through mLDP tunnel 2.

5. PE 2 decapsulates the MPLS packet and then forwards the multicast packet to CE 2.

In inter-AS option A, PEs in different ASs cannot advertise Source Active A-D routes to each other. Therefore, you must configure MSDP or Anycast-RP between RPs to allow Source Active A-D routes to be advertised across ASs.

Inter-AS option B mLDP-based MVPN

As shown in Figure 4:

· A VPN instance spans AS 100 and AS 200.

· PE 3 and PE 4 are the ASBRs for AS 100 and AS 200, respectively.

· PE 3 and PE 4 are interconnected through MP-EBGP and treat each other as a P device.

· PE 3 and PE 4 advertise VPN-IPv4 routes to each other through MP-EBGP.

Figure 4 Inter-AS option B mLDP-based MVPN

To implement inter-AS option B mLDP-based MVPN, only one MVPN needs to be established across all ASs. VPN multicast data is transmitted across the ASs through this MVPN.

Multicast packets of the VPN instance are transmitted as follows:

1. Upon receiving a multicast packet of a multicast group in the VPN instance, CE 1 advertises the RP information for this group to PE 1 as follows:

¡ If the RP is PE 1, CE 1 directly sends a register message to PE 1 to advertise the RP information.

¡ If the RP is CE 1 or CE 2, CE 1 advertises the RP information to PE 1 through MSDP or Anycast-RP depending on the actual configuration.

2. PE 1 sends a Source Active A-D route to PE 3, PE 4, and PE 2 through BGP.

3. PE 2 sends a C-multicast route to join the multicast group if it has a receiver attached. The C-multicast route will be advertised to PE 4, PE 3, and PE 1 through BGP.

4. Upon receiving the C-multicast route, PE 1 encapsulates the multicast packet into an MPLS packet and then sends the packet to PE 2 through the mLDP tunnel.

5. PE 2 decapsulates the MPLS packet and then sends the multicast packet to CE 2.

Inter-AS option C mLDP-based MVPN

As shown in Figure 5:

· A VPN instance spans AS 100 and AS 200.

· PE 3 and PE 4 are the ASBRs for AS 100 and AS 200, respectively.

· PE 3 and PE 4 are interconnected through MP-EBGP and treat each other as a P device.

· PEs in different ASs establish a multihop MP-EBGP session to advertise VPN-IPv4 routes to each other.

Figure 5 Inter-AS option C mLDP-based MVPN

To implement inter-AS option C mLDP-based MVPN, only one MVPN needs to be created cross all ASs. Multicast data is transmitted across the ASs through this MVPN.

Multicast packets of the VPN instance are delivered as follows:

1. Upon receiving a multicast packet of a multicast group in the VPN instance, CE 1 advertises the RP information for this group to PE 1 as follows:

¡ If the RP is PE 1, CE 1 directly sends a register message to PE 1 to advertise the RP information.

¡ If the RP is CE 1 or CE 2, CE 1 advertises the RP information to PE 1 through MSDP or Anycast-RP depending on the actual configuration.

2. PE 1 sends a source-active A-D route to PE 2 through BGP.

3. PE 2 sends a C-multicast route to join the multicast group if it has a receiver attached. The C-multicast route will be advertised to PE 1 through BGP.

4. PE 1 encapsulates the multicast packet into an MPLS packet and then sends the packet to PE 2 through the mLDP tunnel.

5. PE 2 decapsulates the MPLS packet and then sends the multicast packet to CE 2.

mLDP-based MVPN tasks at a glance

To configure mLDP-based MVPN, perform the following tasks on PEs:

1. Enabling IP multicast routing for a VPN instance

2. Configuring BGP IPv4 MVPN route exchange

3. Configuring BGP IPv6 MVPN route exchange

4. Allowing the device to add extended community attributes to C-multicast routes sent to BGP VPNv4 peers

5. Allowing the device to add extended community attributes to C-multicast routes sent to BGP VPNv6 peers

6. Creating an mLDP-based MVPN instance

7. Creating an MVPN IPv4 address family

8. Specifying the MVPN source interface

9. Enabling inclusive tunnel creation

10. (Optional.) Enabling selective tunnel creation

11. (Optional.) Setting the tunnel switchover delay

12. (Optional.) Enabling inter-AS auto-discovery

Configuring mLDP-based MVPN

Prerequisites for configuring mLDP-based MVPN

Before you configure mLDP-based MVPN, complete the following tasks:

· Configure a unicast routing protocol on the public network.

· Configure MPLS LDP on the public network.

· Configure BGP to enable PEs to mutually establish neighbor relationship.

Enabling IP multicast routing for a VPN instance

1. Enter system view.

system-view

2. Create a VPN instance and enter its view.

ip vpn-instance vpn-instance-name

For more information about this command, see MPLS L3VPN commands in MPLS Command Reference.

3. Configure an RD for the VPN instance.

route-distinguisher route-distinguisher

For more information about this command, see MPLS L3VPN commands in MPLS Command Reference.

4. Return to system view.

quit

5. Enter interface view.

interface interface-type interface-number

6. Associate the interface with the VPN instance.

ip binding vpn-instance vpn-instance-name

By default, an interface is associated with no VPN instance and belongs to the public network.

For more information about this command, see MPLS L3VPN commands in MPLS Command Reference.

7. Return to system view.

quit

8. Enable IP multicast routing for the VPN instance and enter MRIB view of the VPN instance.

IPv4:

multicast routing vpn-instance vpn-instance-name

By default, IP multicast routing is disabled for a VPN instance.

For more information about the commands, see multicast routing and forwarding commands in IP Multicast Command Reference.

Configuring BGP IPv4 MVPN route exchange

1. Enter system view.

system-view

2. Enter BGP instance view.

bgp as-number [ instance instance-name ]

3. Specify a BGP MVPN peer and its AS number.

peer ipv4-address as-number as-number

4. Enter BGP IPv4 MVPN address family view.

address-family ipv4 mvpn

5. Enable BGP to exchange IPv4 unicast routing information with BGP peers.

peer ipv4-address enable

By default, BGP cannot exchange IPv4 unicast routing information with BGP peers.

For more information about this command, see BGP commands in Layer 3—IP Routing Command Reference.

6. (Optional.) Specify the maximum number of routes that a router can receive from a peer or peer group.

peer { group-name | ipv4-address [ mask-length ] } route-limit prefix-number [ { alert-only | discard | reconnect reconnect-time } | percentage-value ] *

By default, the number of routes that a router can receive from a peer or peer group is not limited.

For more information about this command, see BGP commands in Layer 3—IP Routing Command Reference.

7. (Optional.) Configure the BGP Additional Paths feature.

a. Configure the BGP Additional Paths capabilities.

peer { group-name | ipv4-address [ mask-length ] | ipv6-address [ prefix-length ] } additional-paths { receive | send } *

By default, no BGP Additional Paths capabilities are configured

b. Set the maximum number of Add-Path optimal routes that can be advertised to a peer or peer group.

peer { group-name | ipv4-address [ mask-length ] | ipv6-address [ prefix-length ] } advertise additional-paths best number

By default, a maximum number of one Add-Path optimal route can be advertised to a peer or peer group.

c. Set the maximum number of Add-Path optimal routes that can be advertised to all peers.

additional-paths select-best best-number

By default, a maximum number of one Add-Path optimal route can be advertised to all peers.

For more information about the commands in this step, see BGP commands in Layer 3—IP Routing Command Reference.

8. (Optional.) Advertise the COMMUNITY or Large Community attribute to a peer or peer group.

¡ Advertise the COMMUNITY attribute to a peer or peer group.

peer { group-name | ipv4-address [ mask-length ] } advertise-community

By default, the COMMUNITY attribute advertisement to a peer or peer group is disabled.

¡ Advertise the Large Community attribute to a peer or peer group.

peer { group-name | ipv4-address [ mask-length ] } advertise-large-community

By default, the Large Community attribute advertisement to a peer or peer group is disabled.

For more information about the commands in this step, see BGP commands in Layer 3—IP Routing Command Reference.

9. (Optional.) Disable route target filtering of received BGP IPv4 MVPN routes.

undo policy vpn-target

By default, a PE device filters route targets for received BGP IPv4 MVPN routes.

10. (Optional.) Set the optimal route selection delay timer.

route-select delay delay-value

By default, the optimal route selection delay timer is 0 seconds, which means optimal route selection is not delayed.

For more information about this command, see BGP commands in Layer 3—IP Routing Command Reference.

11. Prefer routes learned from the specified peer or peer group during optimal route selection.

peer { group-name | ipv4-address [ mask-length ] | ipv6-address [ prefix-length ] } high-priority [ preferred ]

By default, BGP does not prefer routes learned from any peer or peer groups during optimal route selection.

For more information about this command, see BGP commands in Layer 3—IP Routing Command Reference.

12. (Optional.) Prefer BGP routes of a specific next hop IP type during optimal route selection.

bestroute nexthop-priority { ipv4 | ipv6 } [ preferred ]

By default, BGP prefers routes with IPv4 next hops during optimal route selection.

For more information about this command, see BGP commands in Layer 3—IP Routing Command Reference.

Configuring BGP IPv6 MVPN route exchange

1. Enter system view.

system-view

2. Enter BGP instance view.

bgp as-number [ instance instance-name ]

3. Specify a BGP MVPN peer and its AS number.

peer ipv6-address as-number as-number

4. Enter BGP IPv6 MVPN address family view.

address-family ipv6 mvpn

5. Enable BGP to exchange IPv6 unicast routing information with dynamic BGP peers.

peer ipv4-address enable

By default, BGP cannot exchange IPv6 unicast routing information with dynamic BGP peers.