Sunday, August 19, 2012

Cisco/Brocade: How To Find A Computer When You Dont Know Where It Physically Is Or Dont Know Where It Is

Have you ever needed to track down where a computer/server was physically located?  When all you know is the computer name or the IP address, this can be hard to do.  But, on some switching gear, you can run a couple of commands to find your way to the missing device.  Lets say you are looking for a computer named "Alabama01".  The first thing to do is ping Alabama01 and find out what its IP address is.  Hopefully the entry is in DNS, so that you get a look up and the device replies back in a command prompt that the device is live and on the network.  You get the echo-reply.  That is good.  You at least know its turned on.  Now lets find it.  Telnet to your switch.  You can do this with a Brocade or Cisco switch.  You first need to find out if you can find the device in your ARP table on the switch.  You can do this with the 'show arp' command in both Cisco and Brocade/Foundry.

6513#sh arp
Internet               2   00c0.9fef.a82b  ARPA   Vlan1

Now that we know the mac-address of the IP address, we can now do a 'show mac-address-table' command to show what interface the device is located on.

6513#show mac-address-table
Legend: * - primary entry
        age - seconds since last seen
        n/a - not available

  vlan   mac address     type    learn     age              ports
*    1  00c0.9fef.a82b   dynamic  Yes        200   Gi10/23


Now, trace down from that interface and you will find your device.