Saiweb

This is something I find myself having to do, more and more lately due to this VoIP roll out.

From windows (xp)

Start > run > cmd

Once the command window is open ping the IP address of the device (this forces your system to do an ARP request and store the device information in the cache, don’t ask me why but microsoft decided it was a good idea not to lookup the information if it isn’t allready in the cache!)

NOTE: Even if the device blocks ICMP, this should still work, run ettercap on your windows network to see just how many times you will see an ARP request along the lines of “WHO HAS xxx.xxx.xxx.xxx”.

Now to get the MAC address type


arp -a xxx.xxx.xxx.xxx


Where xxx.xxx.xxx.xxx is the IP address of the device you just pinged.


C:\Documents and Settings\buzz>arp -a 10.99.1.10

Please note this only works for a device on the same IP range.

If you run two ranges, i.e.

192.168.1.XXX

and

192.168.2.XXX

You will need to make the ARP request from a device bound to that range (servers are especially usefull here).

Just a quick blog about this …

Ever had the problem of having to assign a DHCP reservation with no mac address resolving software on your laptop? (NOOB! haha)

Well … you have software built in if you are using windows XP anyway …

Start > run > cmd

“arp -a” (without quotes)

this will list your current local interfaces and thier MAC addresses.

“arp -a xxx.xxx.xxx.xxx” (without quotes) Where xxx.xxx.xxx.xxx is the target IP address on your LAN, this will resolve the MAC address for that interface.

Nice quick and simple.

Enjoy!

UPDATE: If you get an error “NO Arp entries found” when doing this, just ping the IP address first, assuming you get a response you _should_ be able to use arp to lookup the mac address!