Came in this morning and the mixer line is down. ControlLogix 1756-L71, 1756-EN2T in slot 1, switch is a Cisco IE 3400. The EN2T display scrolls the IP fine but the link LED is off and the switch port LED is amber.

I moved the EN2T's cable to a spare port on the same switch and it came straight back. Moved it back, dead again. IT's console says err-disabled, "psecure-violation". They did a port security rollout Friday night and the other 30 ports on that switch are fine. A new cable made no difference.

IT says the PLC NIC is faulty and sending "bad MACs". It runs fine on the spare port so I'm not sure about that. I swapped that EN2T for a spare two weeks ago, if that matters. Would a module swap two weeks back leave the old MAC stuck on that port, and would IT be able to see that from their end?