BFD one-arm echo

Bidirectional Forwarding Detection (BFD) supports what is known as one-arm echo. This is also known as unaffiliated echo. It does not require both ends of the link to support BFD.

Although it is not stated explicitly, it seems that Cisco doesn’t support this feature. Cisco documentation does state the following about BFD:

Cisco supports the BFD asynchronous mode, in which two routers exchange BFD control packets to activate and maintain BFD neighbor sessions. To create a BFD session, you must configure BFD on both systems (or BFD peers).

This seems to indicate that both ends of the link must support BFD, thus we can come to the conclusion that one-arm echo is not supported.

Links

https://datatracker.ietf.org/doc/draft-ietf-bfd-unaffiliated-echo/