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find a pc by arp table

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Valued Contributor

find a pc by arp table

Hello to all!

I have a problem with IP conflict. Some user, has set his IP manually, bypassing the DHCP.

now i have his mac-address but i try to find it on the switches.

I have 6 Hp 2650 and 2 Hp 5412.

I try by "show arp" but i see only 2 or 3 IP and i have 300 hosts on the network.

I wrong command?

How i can find the port where he is connected?

thanks to all
Mohieddin Kharnoub
Honored Contributor

Re: find a pc by arp table


telnet to one of the switches, and ping this IP, and you will see its ARP registered with the port leading to it.

This port could be an uplink to another switch, again telnet to that switch and do the same thing until you reach to the port on the switch that this guy connect to.

Now because you have a conflict in the IP, you may get a reply from the other, so i suggest you disconnect the good guy to find the bad guy :)

Good Luck !!!
Science for Everyone
Teknisk Drift_1
Occasional Advisor

Re: find a pc by arp table

"Show arp" will show you the MAC-addresses of the switch's own arp-cache. That is, addresses that the switch itself communicates with.

I believe the command you're looking for is "show mac-address" (at least on 2650).

It will list the mac-adresses the switch knows together with the port number on which the address was detected.

Anders :)
Valued Contributor

Re: find a pc by arp table

Thank you Andres!

Good job! :)