duplicate mac address - why?

Gerard Roy · ‎10-06-2008

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

Istvan_Rabai · ‎10-06-2008

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