Reference Guide

Bidirectional Forwarding Detection (BFD) | 109
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 BGP link to determine the appropriate response to the failure condition. The typical
response is usually 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.
Disabling BFD for BGP
To disable a BFD for BGP session with a specified neighbor, enter the neighbor {ip-address |
peer-group-name} bfd disable command in ROUTER BGP configuration mode.
To remove the disabled state of a BFD for BGP session with a specified neighbor, enter the
no neighbor
{ip-address | peer-group-name} bfd disable command in ROUTER BGP configuration mode. The BGP link
with the neighbor returns to normal operation and uses the BFD session parameters globally configured
with the
bfd all-neighbors command or configured for the peer group to which the neighbor belongs.
Using BFD in a BGP Peer Group
If you establish a BFD session for the members of a peer group (neighbor peer-group-name bfd command
in ROUTER BGP configuration mode), members of the peer group may have BFD:
• Explicitly enabled (
neighbor ip-address bfd command)
• Explicitly disabled (
neighbor ip-address bfd disable command)
• Inherited (neither explicitly enabled or disabled) according to the current BFD configuration of the
peer group. For information on BGP peer groups, refer to Configure Peer Groups.
If you explicitly enable (or disable) a BGP neighbor for BFD that belongs to a peer group:
• 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.
• The neighbor inherits only the global timer values that are configured with the
bfd all-neighbors
command (interval, min_rx, and multiplier).
If you explicitly enable (or disable) a peer group for BFD that has no BFD parameters configured (e.g.
advertisement interval) using the
neighbor peer-group-name bfd command, the peer group inherits any
BFD settings configured with the
bfd all-neighbors command.