Hi Jonathan, > Am 09.01.2025 um 15:40 schrieb Jonathan Guy via Macnetworkprog > <macnetworkprog@lists.apple.com>: > > Hi all, > I'm struggling to identify the cause of a really strange issue that has > started to plague our network of Mac devices. We use Cisco switches and have > port security turned on which means any device that registers more than one > MAC address triggers a port violation which then shuts down the port for a > short period of time (5 mins I believe). > > A few months ago we suddenly started get lots of violations from Mac devices > the were all registering additional MAC addresses (2 usually) that all had > the same 6 character prefix (00:00:40). > > So far we've not been able to determine the cause and now getting pretty > desperate and exploring all possible avenues.
Could there be VMs running on the Macs? If a VM shares the host physical network interface it will use its own MAC address. > All we know is that prefix is registered to a company called Applicon from > back in the day but is now shut down. > > Has anyone come across this issue or know of any possible reason why this may > be happening? The only thing somewhat similar and strange was something that happened probably more than 10 years ago. Two Macs (MacBook Pros IIRC) on a LAN would get the same IP. Turned out that for some reason both had the same MAC address 00:00:00:00:00:00 and the DHCP server thus gave them both the same IP. Much fun follows. I think we solved that by reinstalling Mac OS X (as it was called back then). HTH Mike PS. This is not exactly a high traffic mailing list. The last mail was from more than a year ago. So you might want to try other places to ask as well ;-) _______________________________________________ Do not post admin requests to the list. They will be ignored. Macnetworkprog mailing list (Macnetworkprog@lists.apple.com) Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/macnetworkprog/archive%40mail-archive.com This email sent to arch...@mail-archive.com
