site_archiver@lists.apple.com Delivered-To: macnetworkprog@lists.apple.com Dkim-signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=mac.com; s=1a1hai; t=1736437058; bh=J8i6H6MUy9JEcLwOotTr8Il8zhHNcGSNZ0dZ6lTO2V8=; h=Content-Type:Mime-Version:Subject:From:Date:Message-Id:To: x-icloud-hme; b=Tp2WSXwhjIINChIBJEjzJ3KK7tCpIMwoolhKDXSYG1WiEH+450i2eCubKpf7ZcrfI /ioh+2YcH6yw4MCROQvjCVajLDi0bTpqgfROJh7y/5+7uVQi1OuFT50qHl8kNtjer5 XhSD75NsM9u8x8oI7Oswocs1I++mNSpISXjL9JMN7EeZX7uoMPqO0NtUIBLMnkVtSt gO84e8sYQHnGm+24KWr32MkGEQK3JlcNvaaq2fzxpZkEzDmtbj6EHfSJp+zGvHsE4j fjkC4c6iSh/IQ1TuWkS4lX2K3gNUx8z8/HcR8Eyh2l0Ti6Dn/DgmsAgyUxqjtf3wbu z7jAJ5+A5itSg== 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/site_archiver%40lists... This email sent to site_archiver@lists.apple.com