ddoxey ddoxey - 2 months ago 16
Linux Question

Can I determine the current IP from a known MAC Address?

I have a shell script which uses etherwake to wake up a machine on my local network.
After the machine is awake, I'm not sure of the IP address.

While trying to answer my own question I came up with:

ip=$(ping -c 1 hostname | head -1 | awk '{print $3}' | sed 's/[()]//g')


This solution stipulates that I know the hostname of the remote machine, which isn't so onerous.

Is there a way to get the IP if all I know is the MAC address?

Answer

I don't think there is a single command to do this. One hack would be to do a ping scan or a broadcast ping on the subnet and then query the arp table for the IP address of the MAC address. Obviously not an ideal solution. Example:

nmap -sP 192.168.1.0/24 >/dev/null && arp -an | grep <mac address here> | awk '{print $2}' | sed 's/[()]//g'

Here nmap will do a ping scan and populate your arp cache. Once the scan is done, the arp command can be used to print the arp table and then you pull out the IP address with grep/awk. You could try replacing nmap with a broadcast ping, but that probably isn't as reliable.

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