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BFD Protocol Overview

BFD in Action

BFD Study case

Cisco Router Configuration and Demo

Ø BFD is a protocol that 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.

Ø Once detecting a failure, triggers an action in a routing protocolØ There are 2 BFD modes:

Asynchronous : periodically send control packet between peersDemand : send control packet when needed

Two types of hello packetØ BFD control packet : each peer needs to

process the packet

Ø Echo packet : when one peer receive echo packet, it just loop back the echo to the same link without processing packet

Ø ON Distributed Routing Platforms -

a) BFD packets processed at Line card.

b) Hello packets of Routing protocol processed at RP CPU.

ØBFD provides fast BFD peer failure detection times independently of all media types, encapsulations, topologies, and routing protocols OSPF, BGP, HSRP, MPLS LSP, etc.

ØSome vendor product can support static route binding and layer 2 link detection.

ØBy sending rapid failure detection notices to the routing protocols in the local router to initiate the routing table recalculation process, BFD contributes to greatly reduced overall network convergence time

ØBFD session 3-way handshake and tear down process

ØOne BFD session for multiple client protocols or applications.

ØTwo routers are connected to each other across the long distance that have a lot of devices such as switches, transmission devices etc.

ØWhen one link down in the middle, the routers can’t know the link failure immediately, and wait till the dead time interval of the routing protocol

Ø If not using routing protocol, then both router won’t know the link failure between them at all

Two Step for configuring BFD on Cisco Router

ØStep1: BFD Interface level configurationRouter(config-if)# bfd interval 50 min_rx 50 multiplier 5

ØStep2: BFD Routing Protocol Level configurationRouter(config)# router ospf 1 Router(config-router)# bfd all-interfaces