BFD is a simple hello protocol. It is similar to the hello protocol of IS-IS in many aspects. Two devices periodically send BFD detection packets on the channel between them. If one device does not receive the detection packet from the peer within a certain period of time, the device believes that the bidirectional channel to the peer becomes faulty.


IS-IS, in conjunction with BFD, can fast detect the neighboring status. In this manner, IS-IS devices can fast converge.

Example:

Peer System ID : SV_SAV4_NE40E_AR2     Interface : Vlanif2     
TX : 333           BFD State : up      Peer IP Address : 10.248.3.2 
RX : 333           LocDis : 8212           Local IP Address: 10.248.3.1 
Multiplier : 3     RemDis : 8252       Type : L2
Diag : No diagnostic information

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