Finding ip address from a Mac address

[a.mir]

a device connected on a switch port which mac address is known , how to find the ip address for that device.Any help would be appreciated.

[mheusinger · Accepted solution]

Hello,

to get the IP address you need a device, which is Layer3 capable. You can look at the default gateway into the arp cache. The command would be:

"show arp"

You also have the option to search the output for the specified MAC AA-BB-CC-DD-EE-FF

"show arp | include AA-BB-CC-DD-EE-FF"

To be successful you need to make sure the device does have an IP address and did communicate through the default gateway within the ARP timeout of the router.

Hope this helps! Please rate all posts.

Regards, Martin

[a.mir]

yes you are correct about the layer3 device, but this device is connected on a 6509 layer2 switch, if i do a show arp | include AA-BB-CC-DD-EE-FF on a layer 3 device within the private ip network, it still does not find it.

[a.mir]

got it, you are right, i had a different format of the mac address thats why it did not work the first time.all good, i really appreciate your help in it, Thanks.