Find IP address

[newmarket25]

I am home on vacation. Before leaving, we created a new VLAN and moved 2 servers into that VLAN. I forgot to move the 3rd server in! My problem is that I know the IP and name of the server, but not what port it is plugged into (a 3560G switch). Is there anyway to ask the switch "what port is 192.168.1.x in?" or "what port is server BIGRED in?" Or any way to tell by looking at counters or cache or traceroutes? Once I know the port it will be trivial to do a "swicthport access vlan 10" and everyone will be able to hit that server again! I am desperately trying NOT to go in to work! Thanks.

[spilkinton · Accepted solution]

first, you must find out the mac address. You do this by viewing the arp table of the servers default gateway. Assuming the gateway is a cisco device, the command would be:

sh ip arp | include 192.168.1.x

That will return the mac-address

Then you issue this command on the switch:

show mac-addresses address xxxx.xxxx.xxxx

That will show you what port the machine is plugged into.

[carl.stevenson]

check the ip arp table for the IP address to MAC "sho ip arp | inc 192.168.1.X" then "sho mac-address address XXXX.XXXX.XXXX" to source the port the mac of your server is being learned

[chrihussey]

If you know the mac address of the server you can query the switch with the "show mac address-table H.H.H" where H.H.H is the 48-bit MAC address.

If that doesn't work for you, you could run the command "show mac address-table interface x/x" for each port on the switch, determine the mac associated with the port and then check for an arp entry in your router with the "sh ip arp | include H.H.H" where H.H.H is the mac associated with each port.

It's not perfect, but if there is a port with a mac address and no arp entry it may be your server.

Good luck