I have a device that goes on the network. I need it's MAC address. There is no label on it. How do I do that? I have no access to the device itself. I can power it on and plug it in to a switch or a laptop, and that's it. There is no serial port or any other way of interfacing with the device.

To stave off the inevitable, but irrelevant, questions... we need the MAC address to "register" it on the network. Then it can get an IP address, and then "somebody else" accesses and configures it. It's a black box to us, but we have to have a MAC to register it. Yes, this is insane, but we did not design the device or decide to ship it without a label :-) Please, no responses about how this makes no sense... we know.

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    Boot the device up, look at your DHCP server logs for the MAC address. – yoonix Jan 19 '16 at 16:22
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    What @yoonix said. Or, look at the CAM table of the switch it's connected to. – EEAA Jan 19 '16 at 16:27
  • Can't - we have no access to the DHCP server. There is an interface for the switch which might show this. But I'm looking for some test that I can positively perform... connect a cable to the device and do X to discover the MAC. If I had a Linux laptop I could install dhcpd, but the only systems I have ready access to are Apple Macs. – John Oliver Jan 19 '16 at 16:39
  • You didn't specify your os. If you run unix you might look to arp-scan – user1700494 Jan 19 '16 at 17:34

Connect to the device via a crossover cable or on the same network segment (preferred) via a switch/hub and run a network sniffer (netmon/wireshark/tcpdump) in promiscuous mode to identify the MAC address of the black box.


Can you download Linux live CD, plug it into your Macintosh, and use dhcpd in Linux to get the MAC address?


If you can connect physically to the device, or at least to the same network segment, you might be able to use

arp -a

to show you the mac address table on your server.

  • being connected to same network segment does not guarantee the presence of entry in the host's arp table – user1700494 Jan 19 '16 at 17:31

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