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Strange MAC address spoofing problem

Last Modified: 2012-05-09
Hi there,
I have a Cisco ASA 5520 firewall, where ethernet0/1 is connected to a cisco catalyst 2960 switch.
I also have a Cisco 3670 router, connected to the same switch. The Cisco router terminates several frame relay connections.

Randomly, I see entries such as this on my cisco router when I issue the sh arp command:

Internet        17   0f3b.d8bd.4162  ARPA   Vlan2

The Vlan2 interface on my router is the one connected to the catalyst switch, and the MAC address above belongs to the ethernet0/1 interface on my ASA, so for some reason, although is a frame network connected to an interface on my router, the switch somehow advertises that network to be reachable through my ASA.

I cannot use this guide since my switch OS does not support the vlan access-map command. What would you suggest me to do?

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