How to get a MAC into CAM on L2 switch?

Unanswered Question
Sep 10th, 2010

I have a CAT switch.  When device connects to the port and port says Connected, MAC is not in the CAM table.

It is a DHCP device Arping for it's address.  It will connect with a forced renew or a reboot. 

Why is MAC not added to table?  What can I turn on at the router to see if it gets that far?  I tried dhcp debug but did not see


I have this problem too.
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Federico Coto F... Fri, 09/10/2010 - 15:43

If I understand correctly, you're connecting a device directly on a port of the switch and the MAC is not showing in the MAC table? is this correct?

is the interface up/up? sh inter fasx/x

The MAC address won't show in the address table until there has been something send by that device through the switch (this is the way the switch learns the MAC address from a device).


Lim Seow Hua Sat, 09/11/2010 - 07:42

You can try to issue below command line to get the MAC address of the device that is connected to a particular switch port. See below as example:-

Router> show cam dynamic ?
                   Module number and Port number
                       VLAN number
  |                          Output modifiers

Router> show cam dynamic 3/10
* = Static Entry. + = Permanent Entry. # = System Entry. R = Router Entry.
X = Port Security Entry $ = Dot1x Security Entry M = Mac-Auth-Bypass Entry

VLAN  Dest MAC/Route Des    [CoS]  Destination Ports or VCs / [Protocol Type]
----  ------------------    -----  -------------------------------------------
904   00-11-85-d5-66-a8             3/10 [ALL]

Red highlighted 00-11-85-d5-66-a8 is the mac address. It is the CAT switch which is running CatOS image file.let me know if any.


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