PVST+ HP swtiches

You can connect PVST swtiches to MST swtiches. What happens is that PVST has its own MAC address that the HP swtiches to not listen to, so PVST BPDUs go all they way between the two PVST domains while the MST cloud ignores them. The issue is that the native VLAN must match on the PVST trunk interfaces. The question is how do the swtiches know? As it truns out, PVST BPDUs include a TLV that has the native VLAN number that is how a mismatch is detected. Net of this is that ensure that native VLANs match when you connect PVST switches over a 'cloud' of non PVST swtiches or better yet do to that at all. The reference is at http://www.cisco.com/en/US/tech/tk389/tk621/technologies_tech_note09186a00801d11a0.shtml Troubleshooting Spanning Tree PVID- and Type-Inconsistencies