IOS command to find the IP address of a switchport

Unanswered Question
Jul 7th, 2009

What is the IOS command to find the IP address of a switchport? I have a device connected to a switchport on a known vlan but cannot find the command to show the IP of the device connected to the port. Please help!

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Giuseppe Larosa Tue, 07/07/2009 - 12:41

Hello Kimble,

you need to use two commands

sh mac-address-table interface typex/y

where typex/y is the switchport

then on the L3 device that acts as the default gateway for that vlan/IP subnet

sh ip arp | include

where the MAC is the one listed in first show output

Hope to help

Giuseppe

zzbronski Tue, 07/07/2009 - 12:44

Ok, I tried that and get the following:

flapk001-r02#sh mac-address-table interface fastEthernet 8/6

Legend: * - primary entry

age - seconds since last seen

n/a - not available

vlan mac address type learn age ports

------+----------------+--------+-----+----------+--------------------------

No entries present.

Giuseppe Larosa Tue, 07/07/2009 - 13:02

Hello Kimble,

the CAM entry lasts for 300 seconds this means the device hasn't spoken in the last 300 seconds.

you should do some action for making the device to talk again.

one possible option is to ping the directed broadcast from the default gateway of the vlan.

Clearly you don't control it so the last option (if the ping to directed broadcast doesn't work) is to shut and then unshut the port or better before doing this trying to contact the server administrator

Hope to help

Giuseppe

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