Dell S4048–ON Configuration Manual page 166

• By establishing BFD sessions with all neighbors discovered by BGP (the bfd all-neighbors command).
• By establishing a BFD session with a specified BGP neighbor (the neighbor {ip-address | peer-group-name} bfd
command)
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.
166 Bidirectional Forwarding Detection (BFD)