I have a dumb question about a very dumb device. We have installed a bunch of medical devices to a location and now we need to activate their network function. Device has an embedded OS (unknown) and only shows its IP address on its network menu once connected to a network. On this location i have to provide mac addresses of the devices in order to join them to the network. Manufacturer says only way to see the mac address is to connect it to network and use arp command or check through the network. What would be the fastest way to see the mac address of this device without connecting it to the network on this location? I am considering getting a ethernet enabled mobile modem to resolve this but if there is an easier way it would be very helpful.

Sorry about lack of information on the device but getting a reply from manufacturer takes ages and replies are usually not helpful.

thanks in advance

  • No physical serial number or MAC address on the device? If there's just a serial number, can the manufacturer get the MAC address from their system? Sep 20 at 9:48
  • 1
    Unfortunately no, they said only way was to use arp command on a windows machine connected to same network.
    – MertN
    Sep 20 at 9:55
  • I think they're fobbing you off. All medical devices will need to be calibrated, so will have a serial number that NIST-compliant facility will use in their calibration records. The vendor should have all the details on file, sounds like they can't be bothered to go find the information you require. Sep 20 at 10:22
  • Can't you connect the device to a local computer in order to use arp?
    – harrymc
    Sep 20 at 13:00
  • @spikey_richie you are probably right but this is time-sensitive and they are what they are (reason not to always go with the cheapest option i guess).
    – MertN
    Sep 21 at 14:35

ARP is your friend. Every device (even without an IP) is sending ARP broadcasts. Your device will save these in an ARP table.

Connect a Windows or Linux device via Ethernet to the device and run

arp -a

in the terminal/cmd. This lists all the devices, with their respective MAC-Adresses

You can connect the device with just one cable directly to your windows/linux workstation


  • 1
    There's here a chicken-egg problem: The MAC address is required to allow the device on the network, but without it joining the network arp can't help. Your answer does not address the poster's problem.
    – harrymc
    Sep 20 at 12:59
  • @harrymc no, the device only needs to be connected through an Ethernet cable. It doesn't need an IP address for that. So the MAC address is not needed. Just plug the cable into the device and the other end into the windows/linux workstation :)
    – Nicicalu
    Sep 20 at 13:04
  • Hi thanks for this help unfortunately when i tried direct connection with this particular device all i got was ff:ff:ff:ff:ff as mac address. When i tried a printer to check though it worked. I guess this particular device is just not willing to cooperate with me.
    – MertN
    Sep 21 at 14:31

Do I understand it correctly: in order to get the device into the network you need it’s MAC-address, and in order to get the MAC-address it needs to be in a network, right? So the only option I can come up with is to use a different network to the one you want to put it into, like your phone’s mobile hotspot. Connect the device to your phone or any other WiFi broadcasting device, many laptops can do that as well, get the information you need and then configure the primary network to allow the now known MAC-address.

  • Thanks for the reply, this is what i am planning as this particular device only has ethernet for connection i ordered a lte modem with ethernet port. Hopefuly it will allow me to get this done.
    – MertN
    Sep 21 at 14:33
  • Then I would recommend to use a cross over cable and your laptop. That is probably cheaper and easier to use than an LTE modem. Sep 21 at 15:15

If you can plug directly into the device, you can use tcpdump or wireshark to monitor the traffic. Part of the traffic will be its MAC address.

If you can setup a DHCP server, when it hands out an IP it should record its MAC address.

Some DHCP servers you have to view a log file.

Raspberry Pi has


It will list the IP and MAC address.

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