Reference Guide

Bidirectional Forwarding Detection (BFD) | 167
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 S5000, 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 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.
You can configure BFD for BGP on the following types of interfaces: physical port (10GE or 40GE), port
channel, and VLAN.
To establish a BFD session with one or all BGP neighbors, follow these steps:
Step Task Command Syntax Command Mode
1 Enable BFD globally. bfd enable CONFIGURATION
2 Specify the AS number and enter ROUTER
BGP configuration mode.
router bgp as-number CONFIGURATION
3
Add a BGP neighbor or peer group in a
remote AS.
neighbor {ip-address | peer-group
name}
remote-as as-number
CONFIG-ROUTER-
BGP
4
Enable the BGP neighbor. neighbor {ip-address |
peer-group-name}
no shutdown
CONFIG-ROUTER-
BGP
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.
bfd all-neighbors [interval millisecs
min_rx millisecs multiplier value role
{active | passive}]
OR
neighbor {ip-address |
peer-group-name}
bfd
CONFIG-ROUTER-
BGP
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.
- The neighbor only inherits the global timer values configured with the
bfd all-neighbors command (interval,
min_rx, and multiplier).