Lost the Static IP/network settings of a device

Question

We have a physical device (lab instrument) that we can only connect to via ethernet. Unfortunately a static IP was set with network settings and these settings has been lost.

We connected our computer to the device directly via ethernet. We tried different static IP address settings for the computer so as DHCP, with no avail.

It is not possible to reset the device to factory settings.

The only information we have is the MAC address of the device ethernet card.

Is there a way to find the static IP of the device?

Answer 1

Assuming the device generates some traffic, you make do a packet capture on a device connected to this machine to check the source IP address.

Answer 2

Since you have the MAC address, if you know in wich subnet the machine is you can use the following method:

• from any device that can reach the subnet, perform a network scan of the subnet. I.E. install nmap then type in a command line nmap <subnet>. Example nmap 192.168.0.0/24
• connect on the router acting as the gateway for this network, in CLI if possible
• on the router check the ARP table. The exact way depend on your router brand / model but most network devices offer this feature.
• look for the mac address in the result. You will have the IP address associated with the MAC address.

Note that the NMAP step may not be needed but it ensures that all alive hosts are populated in the ARP table.

The method given by @TeunVink should also work, but this one may be easier depending on your switch / router features.

Answer 3

The easiest way is to run a packet capture on the directly connected device (Teun beat me to it), assuming there's some unsolicited traffic. Possibly, a ping 255.255.255.255 might be able to elicit some reply.

Alternatively, you might need to run an ARP scan over the full subnet range that the device might be configured with.