Hello Giarto
Indeed BFD one-arm echo is defined by the IEEE standard and doesn’t require both ends of a link to support BFD. It seems that Cisco doesn’t support this feature. I say “it seems” because I have been unable to find it stated explicitly. However, 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.
Cisco supports this feature as well, and you can find out how to apply it at the following Cisco documentation:
I hope this has been helpful!
Laz