[bediger4000]

Why would a MAC address duplication "lock up" your whole network? I would guess that at worst that particular laptop would either intermittently get packets or not get packets at all. Which is bad, but not a "lock up". Other stuff should still work.

[wjholden]

I agree with your assessment. A duplicate MAC address could cause a problem for one device, but it shouldn't have caused a full network outage.

Simply opening WireShark for a few minutes might have helped the poster identify their problem faster. Maybe you would observe the same frame transmitting again and again, maybe you would see corrupted frames, or maybe nothing at all.

[starfallg]

Ethernet switches keep track of which ports have which MAC addresses behind them. This is stored in the CAM table of a layer 2 switch. When duplicate entries occur, this result in MAC address flapping and switches have different ways of handling this, which may result in network instability.

[hypercube33]

It shouldn't but I've seen and had some dell docks corrupt arp tables on my switches

[bediger4000]

Now that, although ugly and wrong, makes sense.

[jonah]

Things like that can cause routing "loops" in your network which can mess up everything, not just the device in question. We've had that issue with "dumb" switches.