Dell PowerEdge FN I/O Module Configuration Guide 9.10(0.0)

Before configuring BFD for BGP, you must first configure BGP on the routers that you want to interconnect.

For example, the following illustration shows a sample BFD configuration on Router 1 and Router 2 that use eBGP in a transit network to interconnect AS1 and AS2. The eBGP routers exchange information with each other as well as with iBGP routers to maintain connectivity and accessibility within each autonomous system.

Figure 1. Establishing Sessions with BGP Neighbors

The sample configuration shows alternative ways to establish a BFD session with a BGP neighbor:

• 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.

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.

You can configure BFD for BGP on the following types of interfaces: physical port (10GE or 40GE), port channel, and VLAN.

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.