Service Manual
Establishing Sessions with BGP Neighbors
Before conguring BFD for BGP, you must rst congure BGP on the routers that you want to interconnect.
For more information, refer to Border Gateway Protocol IPv4 (BGPv4).
For example, the following illustration shows a sample BFD conguration on Router 1 and Router 2 that use eBGP in a transit
network to interconnect AS1 and AS2. The eBGP routers exchange information with each other as well as with iBGP routers to
maintain connectivity and accessibility within each autonomous system.
Figure 19. Establishing Sessions with BGP Neighbors
The sample conguration shows alternative ways to establish a BFD session with a BGP neighbor:
• By establishing BFD sessions with all neighbors discovered by BGP (the bfd all-neighbors command).
• By establishing a BFD session with a specied BGP neighbor (the neighbor {ip-address | peer-group-name} bfd
command)
BFD packets originating from a router are assigned to the highest priority egress queue to minimize transmission delays. Incoming
BFD control packets received from the BGP neighbor are assigned to the highest priority queue within the control plane policing
(COPP) framework to avoid BFD packets drops due to queue congestion.
BFD noties BGP of any failure conditions that it detects on the link. Recovery actions are initiated by BGP.
BFD for BGP is supported only on directly-connected BGP neighbors and only in BGP IPv4 networks. Up to 128 simultaneous BFD
sessions are supported
As long as each BFD for BGP neighbor receives a BFD control packet within the congured BFD interval for failure detection, the
BFD session remains up and BGP maintains its adjacencies. If a BFD for BGP neighbor does not receive a control packet within the
detection interval, the router informs any clients of the BFD session (other routing protocols) about the failure. It then depends on
the individual routing protocols that uses the BGP link to determine the appropriate response to the failure condition. The typical
Bidirectional Forwarding Detection (BFD)
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