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
Ø Once detecting a failure, triggers an action in a routing protocol
Ø There are 2 BFD modes:
Asynchronous : periodically send control packet between peers
Demand : send control packet when needed
Two types of hello packet
Ø 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
ØBFD session 3-way handshake and tear down
ØOne BFD session for multiple client protocols or
Ø Two routers are connected to each other across the
long distance that have a lot of devices such as
switches, transmission devices etc.
Ø When 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