How to find out the destination of a switch port

Answered Question
Aug 27th, 2007

A few of our network drop was mislabeled. I need to find out which computer is connected to a certain switch port. Please help.

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Correct Answer by sundar.palaniappan about 9 years 3 months ago

Get the MAC address of the computer connected to a certain port using the command;

On CatOS switches: show cam dynamic (port#)

On IOS switches: show mac-address-table dynamic interface (port#)

If you have a database of MAC to Computer name you could then use that information. If you don't have that info then you need to get the IP of the Computer from the ARP table on the gateway router/L3 switch by issuing the command.

Router/L3 switch:

show ip arp (mac_address)

Hopefully with the IP address you can identify the actual Computer.

HTH

Sundar

Jorge I just noticed you responded to this post barely mins before I posted. I am sure our responses should address the original poster's concern.

Correct Answer by JORGE RODRIGUEZ about 9 years 3 months ago

Springman, if you have IOS base switch you can

retreave MAC address off a port from the switc arp table.

e.g. for a machine connected to port 24 do:

switch#show mac-address-table dynamic interface fastethernet0/24

For CATOS switches:

PC connected to port 12 on module 3.

switch(enable) show cam dynamic 3/12

after retreaving MAC address you can reference the arp table from your upstream routers that are directly connected to the switches to get their mapped IP address.

e.g

router#show ip arp xxxx.xxxx.xxxx

where x is the mac address you retreaved from the switches.

With this info you can then trace back from the port switch to the patch pannel .

HTH

Jorge

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Correct Answer
JORGE RODRIGUEZ Mon, 08/27/2007 - 15:34

Springman, if you have IOS base switch you can

retreave MAC address off a port from the switc arp table.

e.g. for a machine connected to port 24 do:

switch#show mac-address-table dynamic interface fastethernet0/24

For CATOS switches:

PC connected to port 12 on module 3.

switch(enable) show cam dynamic 3/12

after retreaving MAC address you can reference the arp table from your upstream routers that are directly connected to the switches to get their mapped IP address.

e.g

router#show ip arp xxxx.xxxx.xxxx

where x is the mac address you retreaved from the switches.

With this info you can then trace back from the port switch to the patch pannel .

HTH

Jorge

Correct Answer
sundar.palaniappan Mon, 08/27/2007 - 15:39

Get the MAC address of the computer connected to a certain port using the command;

On CatOS switches: show cam dynamic (port#)

On IOS switches: show mac-address-table dynamic interface (port#)

If you have a database of MAC to Computer name you could then use that information. If you don't have that info then you need to get the IP of the Computer from the ARP table on the gateway router/L3 switch by issuing the command.

Router/L3 switch:

show ip arp (mac_address)

Hopefully with the IP address you can identify the actual Computer.

HTH

Sundar

Jorge I just noticed you responded to this post barely mins before I posted. I am sure our responses should address the original poster's concern.

springman Tue, 08/28/2007 - 05:14

Thank you all for the answer. This is exactly what I am looking for. Very helpful. Thanks a lot.

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