Implement and troubleshoot bidirectional forwarding detection (BFD)
BFD – RFC 7419
BFD is a detection protocol designed to provide fast forwarding path failure detection times for all media types, encapsulations, topologies, and routing protocols.
BFD is not tied to any routing protocol. A routing protocol can utilize BFD to held detect neighbor failures faster. Enabled at an interface level. Must be configured on both ends of the link
CEF and IP routing is required on the router
Used to detect faults between 2 nodes connected by a link
- Low overhead detection on physical media that doesn’t support failure detection
- 3 way handshake to establish session
- Supports authentication
- Must be explicitly configured
Modes
- Asynchronous
- Periodically send Hellos between each other
- If number of packets are not received, session is considered down
- Demand
- No hellos are exchanged after session is established
- Assumed endpoints have another way to verify connectivity
Echo mode is enabled by default, works with asynchronous BFD
Config
interface [interface] bfd internal [ms] mix-rx [ms] multiplier [interval] bfd interval 50 min_rx 50 multiplier 5 router bgp [as] neighbor [ip] fall-over bfd router eigrp [as] bfd all-interfaces router ospf [pid] bfd all-interfaces
https://www.cisco.com/c/en/us/td/docs/ios/12_0s/feature/guide/fs_bfd.html
https://en.wikipedia.org/wiki/Bidirectional_Forwarding_Detection