Find an unknown static IP + subnet mask of device?
3 steps
- Download, install and start wireshark
- Connect the device to the computer with the cable
- Restart the device (unplug and plug it back to the power line)
In case the device has a static IP, it should(might) broadcast it's IP on the network, which you should detect with the wireshark.
In case the device has dynamic IP set up, it will ask for an IP adress, in which case connecting it to a router or a computer with DHCP server will resolve the issue.
Note, just today I've seen the sys admin use these steps to find out an unknown IP from the device :)
You could try Angry IP Scanner or, if you have a Linux server, use arp-scan.
I recommend netdiscover. You can use it in passive listening mode and detect incoming ARP announcements (using the -p switch) , or just apply some brute force:
netdiscover -S -f -i eth0
Note that this is incredibly fast compared to nmap (maybe I did not tune nmap well enough).
Also that the method suggested in the currently accepted answer (sniffing for ARP announcements using Wireshark) essentially is what the -p mode is doing.