Dell S4048T Configuration Manual page 196

For example, the following illustration shows a sample BFD configuration 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 20. Establishing Sessions with BGP Neighbors
The 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-neighbors
command).
• 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 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 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 to
128 simultaneous BFD sessions are supported
As long as each BFD for BGP neighbor receives a BFD control packet within the configured 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
Bidirectional Forwarding Detection (BFD) 196