Bidirectional Forwarding Detection

Note

Bidirectional Forwarding Detection (BFD) configuration can be performed only by using the CLI. web UI and SNMP (Simple Network Management Protocol) configuration options are not supported for the BFD feature.

In a network device, BFD is presented as a service to its user applications, providing them options to create and destroy a session with a peer device and reporting upon the session status. On 200 Series switches, BGP (Border Gateway Protocol) can use BFD for monitoring of their neighbors' availability in the network and for fast detection of connection faults with them.

BFD uses a simple 'hello' mechanism that is similar to the neighbor detection components of some well-known protocols. It establishes an operational session between a pair of network devices to detect a two-way communication path between them and serves information regarding it to the user applications. The pair of devices transmits BFD packets between them periodically, and if one stops receiving peer packets within detection time limit it considers the bidirectional path to have failed. It then notifies the application protocol using its services.

BFD allows each device to estimate how quickly it can send and receive BFD packets to agree with its neighbor upon how fast detection of failure could be done.

BFD can operate between two devices on top of any underlying data protocol (network layer, link layer, tunnels, etc.) as payload of any encapsulating protocol appropriate for the transmission medium. The 200 Series implementation works with IPv4 and IPv6 networks and supports IPv4/v6 address-based encapsulations.