I understand that there is downward compatibilty of 802.1w to support lagacy spanning-tree 802.1D. But I need to verify whether the following setup is valid. I have a 6500 as the RB running RSTP which is linked via a trunk (802.1Q) connection to a C3750 switch, also running RSTP, then from the 3750 I have another trunk (802.1Q)link connected to C3550, this switch is running ieee spanning tree, is the uplink switch (3750) able to deteremin it is a legacy BPDU coming from the 3550 on a trunk link? (both have vlan1 as the native vlan) How will the other non native vlans react on the uplink C3750? Should the vlans be on separate interfaces on the 3750-3550 links for the C3750 to deteremin that each VLAN are connected to legacy ieee spanning tree.