Reference Guide

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 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: 100 milliseconds, min_rx: 100 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.
Disabling BFD for BGP
You can disable BFD for BGP.
To disable a BFD for BGP session with a specified neighbor, use the first command. To remove the disabled state of a BFD for
BGP session with a specified neighbor, use the second command.
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.
● Disable a BFD for BGP session with a specified neighbor.
ROUTER BGP mode
neighbor {ip-address | peer-group-name} bfd disable
● Remove the disabled state of a BFD for BGP session with a specified neighbor.
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Bidirectional Forwarding Detection (BFD)