2960 Receives it's own BPDU on the exact same port that it went out
We have a 2960. All of the ports have portfast and BPDU Guard enabled. Port 1 goes to a PC. Port 2 goes to another PC. Port 3 goes to port 1 on a hub.
We the take ports 2 and 3 on the hub and loop them into each other. So the hub has a loop, but the switch doesn't.
I figured that the switch would see it's own BPDU on the port that it originally sent it on, and go err-disabled or BACKUP/Blocking. However, it did not. Layer 2 traffic started looping around on the hub and blasted back into our network through the uplink to the switch.
Any advice on why this happened or how to stop it.
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