Administrator Guide

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 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.
1. Enable BFD globally.
CONFIGURATION mode
bfd enable
2. Specify the AS number and enter ROUTER BGP configuration mode.
CONFIGURATION mode
router bgp as-number
3. Add a BGP neighbor or peer group in a remote AS.
CONFIG-ROUTERBGP mode
neighbor {ip-address | peer-group name} remote-as as-number
4. Enable the BGP neighbor.
CONFIG-ROUTERBGP mode
neighbor {ip-address | peer-group-name} no shutdown
5. Configure parameters for a BFD session established with all neighbors discovered by BGP. OR Establish a BFD session with a
specified BGP neighbor or peer group using the default BFD session parameters.
CONFIG-ROUTERBGP mode
bfd all-neighbors [interval millisecs min_rx millisecs multiplier value role {active |
passive}]
OR
neighbor {ip-address | peer-group-name} bfd
NOTES:
● When you establish a BFD session with a specified BGP neighbor or peer group using the neighbor bfd command, the
default BFD session parameters are used (interval: 200 milliseconds, min_rx: 200 milliseconds, multiplier: 3 packets, and
role: active).
● When you explicitly enable or disable a BGP neighbor for a BFD session with the neighbor bfd or neighbor bfd
disable commands, the neighbor does not inherit the BFD enable/disable values configured with the bfd all-
neighbors command or configured for the peer group to which the neighbor belongs. Also, the neighbor only inherits
the global timer values configured with the bfd all-neighbors command (interval, min_rx, and multiplier).
6. Repeat Steps 1 to 5 on each BGP peer participating in a BFD session.
Establishing Sessions with BGP Neighbors for Nondefault VRF
To establish sessions with either IPv6 or IPv4 BGP neighbors for nondefault VRFs, follow these steps:
1. Enable BFD globally.
CONFIGURATION mode
bfd enable
2. Specify the AS number and enter ROUTER BGP configuration mode.
CONFIGURATION mode
router bgp as-number
3. Specify the address family as IPv4.
CONFIG-ROUTERBGP mode
address-family ipv4 vrf vrf-name
4. Add an IPv4 BGP neighbor or peer group in a remote AS.
CONFIG-ROUTERBGP_ADDRESSFAMILY mode
neighbor {ip-address | peer-group name} remote-as as-number
5. Enable the BGP neighbor.
CONFIG-ROUTERBGP_ADDRESSFAMILY mode
neighbor {ip-address | peer-group-name} no shutdown
158
Bidirectional Forwarding Detection (BFD)