For example, the following illustration shows a sample BFD configuration on Router 1 and Router 2 that useeBGP in a transit network to interconnect AS1 and AS2. The eBGP routers exchange information with eachother as well as with iBGP routers to maintain connectivity and accessibility within each autonomous system.Figure 16. Establishing Sessions with BGP NeighborsThe sample configuration 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-neighborscommand).• By establishing a BFD session with a specified 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 minimizetransmission delays. Incoming BFD control packets received from the BGP neighbor are assigned to thehighest priority queue within the control plane policing (COPP) framework to avoid BFD packets drops due toqueue congestion.BFD notifies 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 to128 simultaneous BFD sessions are supportedAs long as each BFD for BGP neighbor receives a BFD control packet within the configured BFD interval forfailure detection, the BFD session remains up and BGP maintains its adjacencies. If a BFD for BGP neighbordoes not receive a control packet within the detection interval, the router informs any clients of the BFDBidirectional Forwarding Detection (BFD) 181
