[c-nsp] Switch mac address appearing in a VLAN going through it

[Kristofer Sigurdsson]

Hi,

I have the following setup:

7301 <-> Cat3550-12G <-> Cat3750

The link between the 3550 and the 7301 is a 802.1q trunk, native vlan
1.  It has two VLANs in use, 2 and 3.  On the 3550, there is a layer 3
interface (vlan3), which is used for management and OSPF (this is an
"IP Services" (EMI) image, with ip routing enabled).  The 3550 does
not have a vlan2 layer 3 interface.  The 3750 is connected to an
access port on the 3550, which is configured on VLAN2 on the 3550
side.  The interface in the 3550 towards the 3750 has cdp disabled,
bpdufilter and bpduguard enabled and spanning-tree is disabled on VLAN
2.  Additionally, the port in the 3550 is configured as "spanning-tree
portfast".

Now, with this setup, I should only see the 7301's mac address coming
in on the 3750, right?   For some reason or another, when looking at
the mac address table for the port in the 3750, I see two mac
addresses, the 7301 and one of the switch's internal ("CPU") mac
addresses.

Am I mistaken in believing that if a VLAN only goes "through" a
switch, the switch's mac address shouldn't appear in the mac address
table of other switches (on that VLAN)?