Dual PIM Multicast VPNs

In the unicast environment for Layer 3 virtual private networks (VPNs), all VPN state information is contained within the provider edge (PE) routers. However, with multicast for Layer 3 VPNs, PIM adjacencies are established in one of the following ways:

• You can set PIM adjacencies between the customer edge (CE) router and the PE router through a VPN routing and forwarding (VRF) instance at the [edit routing-instances instance-name protocols pim] hierarchy level. You must include the vpn-group-address statement at this hierarchy level, specifying a multicast group. The RP listed in the VRF-instance is the VPN customer RP (C-RP).
• You can also set the master PIM instance and the PE's IGP neighbors by configuring statements at the [edit protocols pim] hierarchy level. You must add the multicast group specified in the VRF instance to the master PIM instance. The set of master PIM adjacencies throughout the service provider network makes up the forwarding path that becomes an RP tree rooted at the service provider RP (SP-RP). Therefore, provider (P) routers within the provider core must maintain multicast state information for the VPNs.

For this configuration to work properly, you need two types of RP routers for each VPN:

• A VPN C-RP—An RP router located somewhere within the customer VPN
• An SP-RP—An RP router located within the service provider network

  Note: A PE router can act as an SP-RP or the VPN C-RP of a VPN. However, when auto-RP and BSR are used, the PE cannot be a C-RP. It can, however, learn another router as C-RP by means of the auto-RP or BSR protocols.

For more information about configuring multicast for Layer 3 VPNs using dual PIM, see Configuring Any-Source Multicast for Draft-Rosen VPNs. For multicast Layer 3 VPN examples, see Example: Configuring PIM Sparse Mode over Layer 3 VPNs.

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