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static vs dynamic CAM entries

Hi,

I am trying to understand the appearance of static CAM entries on a CatOS switch when an IP phone + user PC is connected.

As expected I see the end host(PC), plus IP phone MAC in the CAM table as a dynamic entry. But I also see a static CAM entry, I guess its the MAC of the IP phone's switch.

Looking at the output of "sh cam dynamic x/x" the listed 'destination port' for the addresses is the switch access port the devices are connected to, thats a given.

However the auto detected/generated static address in the CAM table has a destination of multiple ports, all of which seem to be the trunk uplinks to distribution switches. Second the static cam entry uses an unusual MAC, begining with 01 instead of 00.

Can anyone ellaborate on this behaviour, and the unusual MAC address?

I ran a quick test connecting several different switches to the catalyst access port and all of them appear to create a 'static' entry in the CAM table on the catalyst 65xx, using a MAC starting with 01x.

Thanks,

1 REPLY

Re: static vs dynamic CAM entries

show cam dynamic are just what they are mac-addresses learned by the switch dynamically through the traffic generated by these devices using the source mac-address. The mac-addresses on show cam static are multicast L2 mac-address like 01-00-5e-00-xx-xx. You will see the same mac-address with show multicast group. It does not mean someone or the system had configure a static cam entry otherwise you will see a "*" for that static entry.

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