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About Bidirectional Forwarding Detection (BFD)


Bidirectional forward detection (BFD) is the protocol designed for detecting fast forwarding path failure detection various media types, encapsulations, topologies and routing protocols. BFD helps in providing a consistent failure detection method. 

In NSX-T environment where Edge node in edge cluster exchange its BFD keep-alive status on management and tunnel (TEP/overlay) interface to get proper communication among each Edge/host transport nodes in NSX-T environment.

                                                      Fig:1 (Credit:

eg: When the standby Edge node on T0 gateway fails to receive keep-alive status on both (management & tunnels) interfaces then in that case its not going to become active as its already in standby state. What its looses is its interface communication either from management of overlay.

Some features of BFD 

  • High availability uses BFD to detect forwarding path failures.
  • BFD provides a low-overhead detection of fault even on physical media that do not support failure detection of any kind, suck as Ethernet.
  • BFD keep alive were sent to both management and tunnel interfaces.

                                                                       Fig:2 (Credit:

  • The Tier-0 gateway supports the BFD protocol to protect the connection within the routing peers (External/physical).
  • BFD allows and protect both static and dynamic routers.
  • Provides fast detection of node (edge or physical gateway) or uplink failures.
  • Enable multiple BFD sessions if multiple link exist between two system.


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