Service Manual

As long as each BFD for BGP neighbor receives a BFD control packet within the congured 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 conguration 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. Congure parameters for a BFD session established with all neighbors discovered by BGP. OR Establish a BFD session with a
specied 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 specied 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 congured with the bfd all-
neighbors command or congured for the peer group to which the neighbor belongs. Also, the neighbor only inherits the
global timer values congured 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 specied neighbor, use the rst command. To remove the disabled state of a BFD for BGP
session with a specied neighbor, use the second command.
The BGP link with the neighbor returns to normal operation and uses the BFD session parameters globally congured with the bfd
all-neighbors command or congured for the peer group to which the neighbor belongs.
• Disable a BFD for BGP session with a specied neighbor.
ROUTER BGP mode
neighbor {ip-address | peer-group-name} bfd disable
Bidirectional Forwarding Detection (BFD)
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