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Community Member

Find IP based on switchport if arp table is not populated with IP

Hi, my goal is to find out which device IP address is connected to port f0/10. Here is what I have done:

sw#show mac-address-table

Mac Address Table

-------------------------------------------

Vlan Mac Address Type Ports

---- ----------- -------- -----

4 001a.dd75.3e70 DYNAMIC Fa0/10

4 001x.dd75.3deb DYNAMIC Fa0/11

4 0022.1cd4.cd30 DYNAMIC Fa0/9

sw#show arp | i 001a

Nothing is listed, 'show arp' lists no mac address and IP associated with port f0/10.

Question:

Is there any benign way to trigger device connected to f0/10 port to update arp (and resolve IP) so that I can identify

the respective IP address?

1 ACCEPTED SOLUTION

Accepted Solutions
Hall of Fame Super Blue

Re: Find IP based on switchport if arp table is not populated wi

Marlon

The device that you need to run the "sh arp" command is the device that is routing for the vlan. So is the switch you are on in your example a L3 switch ?. If not you need to log on to the L3 device that routes the client vlan and run your arp there.

If it a L3 switch then just ping the device.

Jon

2 REPLIES
Hall of Fame Super Blue

Re: Find IP based on switchport if arp table is not populated wi

Marlon

The device that you need to run the "sh arp" command is the device that is routing for the vlan. So is the switch you are on in your example a L3 switch ?. If not you need to log on to the L3 device that routes the client vlan and run your arp there.

If it a L3 switch then just ping the device.

Jon

Community Member

Re: Find IP based on switchport if arp table is not populated wi

Oh, my bad. That is it.

Thanks!!

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