Reference Guide

Bidirectional Forwarding Detection (BFD) | 141
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 7-15. BFD Session Between BGP Neighbors
Note that 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 (
bfd all-neighbors command)
• By establishing a BFD session with a specified BGP neighbor (
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.
• On an E-Series ExaScale, up to 100 simultaneous BFD sessions are supported.
• On an S4810, up to 64 simultaneous BFD sessions are supported.
AS 1
AS 2
Router 1
Router 2
Interior BGP
Exterior BGP
Interior BGP
1/1
2.2.4.3
FTOS(conf)# bfd enable
FTOS(conf)# router bgp 2
FTOS(conf-router-bgp)# neighbor 2.2.4.2 remote-as 1
FTOS(conf-router-bgp)# neighbor 2.2.4.2 no shutdown
FTOS(conf-router-bgp)# bfd all-neighbors interval 200 min_rx 200
multiplier 6 role active
OR
FTOS(conf-router-bgp)# neighbor 2.2.4.2 bfd
FTOS(conf)# bfd enable
FTOS(conf)# router bgp 1
FTOS(conf-router-bgp)# neighbor 2.2.4.3 remote-as 2
FTOS(conf-router-bgp)# neighbor 2.2.4.3 no shutdown
FTOS(conf-router-bgp)# bfd all-neighbors interval 200 min_rx 200
multiplier 6 role active
OR
FTOS(conf-router-bgp)# neighbor 2.2.4.3 bfd
2/2
2.2.4.2