Cisco Catalyst – Find out What Port an IP Address is Plugged Into

KB ID 0001022 


I networked some gear this afternoon, and I made a mental note of the ports I patched into on the switch. On the way back to the office I got side-tracked. By the time I got back to my desk I could not remember what port I had used, and I wanted to add a description to the port.

bad wiring

This is not my server room 🙂

So I knew the IP address but not the port number, how can you find that out?


1. My IP address is, let’s ping that from the switch.

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to, timeout is 2 seconds:
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/5/17 ms

2. Well I can ping it so, there must be an entry in my ARP cache, and I can find the MAC address for that IP.

Petes-Switch#show ip arp
Protocol Address Age (min) Hardware Addr Type Interface
Internet 5 0080.a394.e2de ARPA Vlan100

3. Armed with the MAC address I can take a peek in the MAC Address table.

Petes-Switch#show mac address-table address 0080.a394.e2de
Mac Address Table

Vlan Mac Address Type Ports
---- ----------- -------- -----
40 0080.a394.e2de DYNAMIC Gi0/40 <<Boom! there it is!
Total Mac Addresses for this criterion: 1

Note: I knew that my device was a single device plugged into a port, but if you don’t know this, there is a chance that the physical port you track down, might just be the uplink to another switch, that your device is plugged into. Or you’re at the end of a lot of switches, this is just the next step towards your device). If that is the case you would have several MAC addresses on that physical port, like so;

Petes-Switch##show mac address-table interface GigabitEthernet 0/48
Mac Address Table

Vlan Mac Address Type Ports
---- ----------- -------- -----
40 6412.25ea.ca80 DYNAMIC Gi0/48
40 d072.dcac.becc DYNAMIC Gi0/48
120 6412.25ea.ca80 DYNAMIC Gi0/48
120 d072.dcac.becc DYNAMIC Gi0/48
122 6412.25ea.ca80 DYNAMIC Gi0/48
122 d072.dcac.becc DYNAMIC Gi0/48
121 6412.25ea.ca80 DYNAMIC Gi0/48
121 d072.dcac.becc DYNAMIC Gi0/48
Total Mac Addresses for this criterion: 8

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Author: Migrated

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