[CentOS] find IP address of device on network based on MAC address

Milton Calnek milton at calnek.com
Fri Dec 14 21:11:22 UTC 2007



Brian wrote:
> 
> On Dec 14, 2007, at 3:21 PM, Les Mikesell wrote:
> 
>> Jerry Geis wrote:
>>> I have a device on my network that is not DHCP and I dont know the IP 
>>> address of it
>>> and it has not method of finding it or changing it unless you know 
>>> the IP address (setable by browser).
>>> Is there a way on linux, based on MAC address, to get the IP of the 
>>> unit?
>>
>> You accumulate a table of mac<->ip assocations, but only after 
>> communicating with something.  arp -a will show the current entries 
>> (which expire fairly quickly).  You might ping everything in the 
>> network range, then look for the mac in the arp list.
> 
> to ping every address, check out broadcast pings here
> 
> http://www.macworld.com/article/53277/2006/10/pingfind.html
> (or google other how-to's)

The tool you want is fping.  It's available from the rpmforge repository.

fping -ga 192.168.c.d/m
arp -n | grep aa:bb:cc:dd:ee:ff

Now you may have two problems:
1. The unknown device is not in your address space. ie: your net is 
192.168.0.0/24 and the ip of the device is 192.168.1.1.
2. Your mask is too large. ie: 192.168.0.0/20 may be too large for you 
to scan the entire address space before your arp tables runs out of room.

Good luck.

-- 
Milton Calnek BSc, A/Slt(Ret.)
milton at calnek.com
306-717-8737


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