[jnojr]

I got an email from a user saying that he used to be able to (a long time ago)

arping -I eth0 00:1a:64:c2:cg:5a

and get the IP address of the MAC. Now, he can't. I've tried on a couple of different Linux systems, and it doesn't work for me, either. Anyone know what's up with this? The man page doesn't help... it seems to indicate that the above should work just fine.

[HROAdmin26]

An ARP request is a broadcast to *find* the MAC address when the IP address is known.

Thus, usage is:

arping -I eth0 <ip_address>

arping -I eth0 10.66.91.5
ARPING 10.66.91.5 from 10.66.91.240 eth0
Unicast reply from 10.66.91.5 [00:C0:9F:3D:35:01]  0.767ms
Unicast reply from 10.66.91.5 [00:C0:9F:3D:35:01]  0.758ms
Unicast reply from 10.66.91.5 [00:C0:9F:3D:35:01]  0.765ms
Sent 3 probes (1 broadcast(s))
Received 3 response(s)

Address Resolution Protocol

And further info:

There are two arping implementations. One is part of Linux iproute2, is Linux-only, and cannot currently ask who has what MAC address. The other arping implementation by Thomas Habets uses libpcap and libnet to be platform independent, and works on lots of UNIX-based OSs and even Windows.

[jnojr]

OK... if his syntax is wrong, how do you get the IP associated with a given MAC without access to any switches?

[HROAdmin26]

Originally Posted by HROAdmin26

And further info:

There are two arping implementations. One is part of Linux iproute2, is Linux-only, and cannot currently ask who has what MAC address. The other arping implementation by Thomas Habets uses libpcap and libnet to be platform independent, and works on lots of UNIX-based OSs and even Windows.

From that page:

Arping from T.Habets:

arping2 00:01:80:38:F7:4C
arping2 192.168.39.120

And from that page, an external link.

Note: I don't know what OS/distro you're using and I don't know *what* packages you have installed, etc. If your current arping utility doesn't support querying by MAC, get T. Habets'. Or use some other network utility. All of this info was found via Google.