duplicate mac address - why?

Unanswered Question
Oct 6th, 2008

Can anyone explain why I have duplicate MAC addresses? It is a 1711 router with NAT and should VLAN1 adopt the mac of the LAN switch interface it is plugged into?

Internet 67.234.10.95 - 0016.c791.73de ARPA FastEthernet0

Internet 192.168.1.1 - 0016.c791.73de ARPA Vlan1

I have this problem too.
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Istvan_Rabai Mon, 10/06/2008 - 18:37

Hi Jerry,

As far as I understand from your post, FastEthernet0 and VLAN1 are in different subnets, and in different vlans.

In this case this should cause no problems to have the same mac-address on different interfaces.

Multilayer switches regularly use the same mac-address on different vlan interfaces.

A layer2 address is used only within the boundaries of that layer2 domain.

Cheers:

Istvan

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