Frame-Relay interface stuck looped

[JohnWocher0825]

I find many frame-relay interfaces on ISP edge routers to become stuck looped after loop testing the circuit with local providers.

After confirming providers to drop their loopbacks, at a relatively high percent need to shut / no shut the interfaces to clear the loopback.

I have found this only happens to frame-relay configured interfaces, can someone explain the mechanism.

[Peter Paluch]

Hello John,

Sorry for the late reply.

I am not sure why some interfaces need to be shut/unshut while others do not. Nevertheless, I can imagine that on those interfaces where no such procedure was needed, actually the removal of the local loopback by the service provider caused the interface to lose carrier signal for a moment, resulting in an up/down/up transition, similar to a shut/unshut. I must admit I am not sure if the Frame Relay has any mechanisms to detect a loopback (perhaps via the LMI).

And are you suggesting that this never happens with, say, PPP or HDLC encapsulations? I am still wondering that if the phenomenon is random in nature, you may just had luck with not experiencing it on PPP/HDLC encaps but eventually it could show up on those as well.

Could this explain your situation?

Best regards,

Peter