[nycbug-talk] Finding a device's IP address

[Pete Wright]

On 19-Mar-09, at 3:52 PM, Charles Sprickman wrote:

> Perhaps a bit OT, but a general question...
>
> You have a device on a network that you do not have physical access  
> to.
> It has an IP address which may or may not be on the subnet it's  
> actually
> attached to.
>
> How do you find what IP is configured?  What magic ARP stuff can you  
> spew
> in it's direction that would perhaps make it respond with something  
> that
> would give away it's IP?

in the past when i've been in this pickle i logged into a switch i  
suspected was close to the host in question.  found its entry in the  
arp cache (which was associated w/another switch).  connected to that  
switch, washed hands repeated until i found the subnet that the box  
was on (in this case our IBM nodes all had a similar range of mac  
addy's which was sufficiently different than our foundry switches  
which made things easier).


there's even a fun diagram i found online:
http://www.networkblueprints.com/troubleshooting/using-mac-address-table-and-arp-cache-lan

HTH
-p