Administrator Guide

Figure 15. 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 in both BGP IPv4 and IPV6 networks. Up to 200 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 session (other routing protocols) about the failure. It then depends on the individual
routing protocols that uses the BFD link to determine the appropriate response to the failure condition. The typical response is to
terminate the peering session for the routing protocol and reconverge by bypassing the failed neighboring router. A log message is
generated whenever BFD detects a failure condition.
Prerequisites
Before configuring BFD for BGP, you must first configure the following settings:
• Configure BGP on the routers that you want to interconnect.
Establishing Sessions with BGP Neighbors for Default VRF
To establish sessions with either IPv6 or IPv4 BGP neighbors for the default VRF, follow these steps:
1. Enable BFD globally.
CONFIGURATION mode
bfd enable
144
Bidirectional Forwarding Detection (BFD)