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Community Member

Duplicate MAC addresses for same device

Why do I see duplicate entries in the mac address table on different vlans for the same mac address. This is seen with an Avaya phone that boots on the data vlan and then changes to the voice vlan after receiving registration parameters.

Is this seen as 2 entries on the port as far as port-security or maximum cam table entries is concerned?

3 REPLIES
Cisco Employee

Re: Duplicate MAC addresses for same device

This is normal, the IP phone's mac should show you in both the data vlan and voice vlan.Yes, this will be seen as 2 entries on the por-security table and you have to increase the max-count to 2 instead of default 1. Otherwise the phone will not work with port-security enabled on the switchport.

When you enable port security on an interface that is also configured with a voice VLAN, you must set the maximum allowed secure addresses on the port to two plus the maximum number of secure addresses allowed on the access VLAN. When the port is connected to a Cisco IP phone, the IP phone requires up to two MAC addresses. The IP phone address is learned on the voice VLAN and might also be learned on the access VLAN. Connecting a PC to the IP phone requires additional MAC addresses.

HTH,Please rate if it does.

-amit singh

Community Member

Re: Duplicate MAC addresses for same device

amit,

Thanks for the reply,

You mentioned this will be seen as 2 entries in the port-security table, does the CAM table see it as 2 entries also?

Thanks, Brian

Cisco Employee

Re: Duplicate MAC addresses for same device

Brian,

The mac-table should see it as two entries as well. One entry in data vlan and one entry in voice vlan for the IP phone's mac.

HTH,Please rate if it does.

-amit singh

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