Re: MAC Address issue
Re: MAC Address issue
- Subject: Re: MAC Address issue
- From: Mike Fischer via Macnetworkprog <email@hidden>
- Date: Thu, 9 Jan 2025 16:37:23 +0100
Hi Jonathan,
> Am 09.01.2025 um 15:40 schrieb Jonathan Guy via Macnetworkprog
> <email@hidden>:
>
> 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 ;-)
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| | >MAC Address issue (From: Jonathan Guy via Macnetworkprog <email@hidden>) |