IP Address discovery on LAN

Question

I've got an Airport Base Station with two wireless clients and one ethernet client. The ethernet client is a device that I'm working on for a client, but the client has yet to tell me what the ip address is configured to. Is there a way to identify said device's ip address?

I do not think that it's using DHCP, rather it's hard wired into the device for the moment.

Answer 1

You may be able to fire up Wireshark on one of the wireless clients - there may be some broadcast traffic from your client's device that gives some clue what its IP is.

Answer 2

How are you working on it? If you're directly on it can't you get the IP address from the OS?

If it's plugged into the network and configured correctly then it should be on the same subnet. A tool like nmap run from one of the other clients will tell you the responsive machines on the network and you can work out which it is.

Answer 3

The documentation for the device should tell you what it's initial IP address is, if it's statically configured by default.

Answer 4

• Unplug the client device from the network.
• Connect the ethernet client to a laptop running Wireshark using a crossover cable. IIRC, this usually works best if you don't have an IP assigned to the laptop interface.
• If you don't immediately see traffic from the device in Wireshark, power the device off then back on.
• When it comes up you should see DHCP or BOOTP requests (if the IP is dynamic), if it has a static IP you should start seeing ARP requests from the device looking for its gateway.
• If you don't see any traffic for the device, you could try using nmap to do an "arp scan" using the -PR option (you may need to assign an IP to your laptop's NIC for this to work and you may need it to be on the same subnet for this to work)

Answer 5

You could give Nmap a try.