STP port receives own bpdu.

[Charlie Grey]

if a cisco switch access port (spanning-tree portfast disable) connect a unmanaged switch, and there is a short btw ports on the unmanged switch, what will happen to the access port? err-disable or blk?

[Francesco Molino]

Hi

Ok let's try to give you a clear answer.
When stp is enabled on the switch, by receiving its own bdpu, it will put the port in blocking state.
Now on interfaces, you have the keepalive capability. This feature will send frame, we call loop frame, and by receiving its own loop frame, the switch will put the interface as err-disable.

In your case, with stp globally enabled, your port will be in blocking.