CHAPTER
19-1
Cisco ASR 901 Series Aggregation Services Router Software Configuration Guide
OL-23826-09
19
Configuring Bidirectional Forwarding Detection
Bidirectional Forwarding Detection (BFD) provides a low-overhead, short-duration method of detecting
failures in the forwarding path between two adjacent routers, including the interfaces, data links, and
forwarding planes. BFD is a detection protocol that you enable at the interface and routing protocol
levels.
Contents
• Understanding BFD, page 19-1
• Configuring BFD, page 19-1
• Configuration Examples for BFD, page 19-7
Understanding BFD
Cisco supports the BFD asynchronous mode, in which two routers exchange BFD control packets to
activate and maintain BFD neighbor sessions. To create a BFD session, you must configure BFD on both
systems (or BFD peers). After you enable BFD on the interface and the router level for the appropriate
routing protocols, a BFD session is created, BFD timers are negotiated, and the BFD peers begin to send
BFD control packets to each other at the negotiated interval.
Configuring BFD
This section contains the following topics:
• BFD Configuration Guidelines and Restrictions, page 19-2
• Configuring BFD for OSPF, page 19-2
• Configuring BFD for BGP, page 19-4
• Configuring BFD for IS-IS, page 19-4
• Configuring BFD for Static Routes, page 19-6
For more information about BFD, refer to the IP Routing: BFD Configuration Guide, Cisco IOS Release
15.1S.