Bidirectional forwarding detection or BFD, in NSX-T (aka NSX 4.x onwards)

In VMware NSX-T (NSX Data Center), BFD stands for “Bidirectional Forwarding Detection.” BFD is a network protocol used to detect and quickly respond to failures in the forwarding path between network devices, such as routers or switches. It is designed to provide rapid failure detection and minimal downtime by quickly detecting link or path failures and notifying the network devices to take appropriate actions. BFD is particularly useful in scenarios where traditional link-state protocols might take longer to detect and respond to failures.Here’s a brief overview of how BFD works in NSX-T:

  1. Fast Failure Detection: BFD is used to monitor the health and availability of network paths or links between NSX-T routers. It sends periodic lightweight control packets called BFD control packets to the neighboring devices.
  2. Bidirectional Communication: BFD uses a bidirectional approach, where both ends of the communication path exchange BFD control packets. This ensures that both devices can quickly detect a failure in either direction of traffic flow.
  3. Detection Times: BFD is designed to detect failures within milliseconds, providing near-instantaneous detection of link or path issues. This rapid detection allows network devices to quickly respond to failures and reroute traffic as needed.
  4. Multi-Hop Support: BFD can be used to detect failures in multi-hop scenarios, where there are multiple intermediate devices between two endpoints. This is useful for detecting failures across complex network topologies.
  5. Compatibility: BFD can work with various routing protocols and network devices, making it a versatile solution for enhancing network reliability and resilience.
  6. BFD in NSX-T: In NSX-T, BFD can be configured to monitor the health of routes between NSX-T logical routers, ensuring that any path failures are quickly detected. When BFD detects a failure, NSX-T can trigger automatic route updates to reroute traffic around the failed path.


BFD in NSX-T helps to improve network availability and reduce downtime by providing fast and efficient detection of link or path failures. It enhances the overall reliability of network communication within the NSX-T environment and ensures that critical applications can continue to operate even in the presence of network issues.

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