Get IP Address from a known MAC Address

I’ve been playing around with networking hardware for the last week or so. I have a bunch of different types of things: several Airport Extremes, a bunch of Airport Expresses, and a smattering of other devices, including one no-brand WiFi extender.

I also have a pcDuino, which I bought when they were still very overpriced.

I was attempting to install a newer version of Debian onto that device today (specifically, Armian). I burned an image to an SD card, and put it in the slot, expecting it to pop up on my network (it should have the same IP address, because I have a fixed lease set aside for that MAC address). However, it didn’t pop up, so I starting digging for it.

The other day I had a similar issue with the no-brand WiFi adapter: it had decided it would have a static IP address (which I may have done ages ago: I’m not sure I ever really set that up though).

I tried a bunch of things to try to get it’s IP address, without success. There was no DHCP record, and I could not find it in any arp -a lists. Then, I happened across a method I had not tried before: using tcpdump:

sudo tcpdump -i en1 -s 0 -v -n ether host aa:bb:cc:dd:ee:ff

Eventually, that showed me what IP address that device was using, and I was able to connect to it by setting a compatible IP address on another device, and using that IP address directly.