CAM Table Duplicate

Answered Question
Jul 21st, 2008
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Guys,


I'm having a problem with some servers losing connectivity randomly. Whenever I clear the arp cache, the problem goes away, but eventually resurfaces. I figure this is a layer 2 issue. So I pull the MAC addresses of the servers of interest and take a look at the CAM table. As I look at the MAC addresses one by one, I notice this for one of the particular MAC addresses of interest:


switch1#sh mac-add add 0011.855c.0959

Legend: * - primary entry

age - seconds since last seen

n/a - not available


vlan mac address type learn age ports

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

Module 12[FE 1]:

* 9 0011.855c.0959 dynamic Yes 5 Gi12/12

Module 12[FE 2]:

* 9 0011.855c.0959 dynamic Yes 60 Gi12/12



Why am I getting two entries for this port, and could this create a problem of any sort? And could anyone explain what 'FE 1' and 'FE 2' is?

Correct Answer by chrismarget about 8 years 9 months ago

It looks like you've got a DFC installed on the card in slot 12.


I think this means that the DFC is keeping its own (extra) copy of the L2 forwarding table.


This is normal.


/chris

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Correct Answer
chrismarget Mon, 07/21/2008 - 11:07
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It looks like you've got a DFC installed on the card in slot 12.


I think this means that the DFC is keeping its own (extra) copy of the L2 forwarding table.


This is normal.


/chris

Ryan Carretta Mon, 07/21/2008 - 23:38
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Chris is correct. Moreover, there are two forwarding engines that maintain their own CAM entries. That's what you're seeing in the [FE1] and [FE2].

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