BPDUs and BPDUGuard

winslade

As I understand BPDUs will go through all switches and also to end devices...
If BPDUGuard and PortFast was enabled on a end device port, I assume the ports will still receive BPDUs, and the port will get disabled.

How can these ports ignore BPDUs when connected to an end device but not if a switch/router attempts to connect to that port?

fredrikjj

The edge port where the end device is connected still sends BPDUs when Guard is enabled, but the end device just drops those BPDUs and doesn't send them back to the switch. However, if for some reason there's a loop from the edge port to a different edge port, that second edge port will receive the BPDUs and BPDU Guard will kick in. It can also be a loop back to the same edge port if you use an unmanaged switch that's connected back into itself.

dontstop

BPDUguard is looking for incoming BPDUs from the edge port. Ones flowing to the edge device are not counted

winslade

Thank you! This clears things up well.
I was under the impression that it included outgoing also