[c-nsp] VLAN 1 troubles?

[John Osmon]

I've got a 3560 switch in a lab situation that I'm looking for insight.

I have a virtualization host hung off of a trunking port.  VMs on this
platform are able to communicate over any VLAN if I'm running a 12.2
image.

As soon as I change to a 15.0 image, packets for VLAN1 no longer pass
the switch port -- but all other VLANs do.  This is true whether the
packets are explicitly tagged as VLAN 1, or if I leave them "native."

I have means to work around the issue, but it's bugging me...

Is there some esoteric change between IOS 12 and IOS 15?
Is there something I've been doing wrong for years with IOS switches?
Am I hitting a bug?
Do I just need to get rid of this test switch and get something more
modern for a lab switch?


Switch details:
 model:         WS-C3560G-24TS
 working image: c3560-advipservicesk9-mz.122-25.SEE2.bin
 failing image: c3560-ipservicesk9-mz.150-2.SE10.bin
 port config:
   interface GigabitEthernet0/15
    switchport trunk encapsulation dot1q
    switchport mode trunk