Tip of the Week: Ethernet to Hostname Mapping With ARP.

Blog Post created by guy_wettstein on Feb 3, 2013

You might find yourself with a license file that has the Ethernet address of your license server but you have no idea which of your network hosts that Ethernet address resolves to. You could labor through a manual verification of every system on your network by loggin in remotely and checking the Ethernet address. On Windows, you might use a network utility like Wireshark (, which might actually work very well. But what if you're on Linux or Solaris? Fortunately, the ARP table can help you solve this problem.


ARP stands for Address Resolution Protocol ( and is the means of address resolution on your network. As network communication between hosts occur, ARP populates a table that contains the physical addresses of the hosts your system is communicating with. While not all hosts are cached in the table at a given time, you can populate the ARP table using ping or arping. Using one of these utilities in a loop can quickly move through all the IP adresses in a subnet and therby populate the ARP table for you.


Once this is done, it rather trivial to grep the ARP table for the Ethernet address you're looking for:


guyw@guyshost$ arp | grep 00:50:56:AB:4D:6E  ether   00:50:56:AB:4D:6E   C                     eth0



So in this case, I now know that 00:50:56:AB:4D:6E resolves to netsrv-lic-o3 and I can proceed with configuring my license server on that system.


There are likely numerous ways to address this problem. Feel free to share your tips with other users in the comments.