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Configuring BIER MVPN

A Bit Forwarding Ingress Router (BFIR) encapsulates the incoming non-BIER multicast packets with the BIER header. For it to know which bit string to use, a multicast flow overlay protocol is needed so that the BFERs can tell BFIRs that the BFERs need to receive certain overlay (for example IP) multicast traffic. This way BFIRs can set up an overlay multicast forwarding state with appropriate BIER encapsulation information. BGP-MVPN is one such multicast overlay protocol, as it already has mechanisms for egress PEs (BFERs) to notify ingress PEs (BFIRs) that the BFERs need to receive traffic for certain (C-S/*, C-G/*).

Configuring BIER Provider Tunnels

You must include the bier statement at the [edit protocols] hierarchy level to enable BIER on the router.

To configure a Bit Index Explicit Replication (BIER) provider tunnel for a multicast VPN, include the bier statement:

You can include this statement at the following hierarchy level:

You can also configure bier for selective provider tunnels by configuring the following statement:

The provider tunnel label should be the same as the configured static vrf-table-label so that this label can be assigned to the lsi interface associated with that routing-instance.

In order to avoid interoperability issues with other vendors, the PMSI length should be the same size as the BIER prefix. It can be either IPv4 or IPv6.

Verifying BIER in MVPN

Issue the show mvpn instance command to display provider tunnel information.

From the output above, it can be seen that two neighbors advertise the BIER tunnel in sub-domain 10 in their I-PMSI A-D routes, with BFR-ID 2 and 3 respectively. This router also advertises a BIER tunnel in sub-domain 10 with its own BFR-ID (1) and label 999901 to identify this VPN.

The I-PMSI tunnel is used for four (S,G) flows and the forwarding next hop used for those flows is a next hop with ID 8169, displayed as M-8169.

Issue the show multicast route extensive instance instance-name command to review those flows in detail.

Push 999901 - this label identifies the VPN.

bier bitstring - the bit string to be encoded in the BIER header. In this example, the 2nd and 3rd bits are set, indicating that these two corresponding BFERs are to receive traffic.

label 800000 - the label that this router advertised for the corresponding BIFT. When the (S,G) packet is received on PE-CE interface, it matches this route so the VPN label is imposed. The BIER header is encoded with the bit string and this label, and then the packet is treated as if the BIER packet was just received on a core interface.

To display the local tunnel name, issue the show multicast route extensive instance instance-name display-tunnel-name command.

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