Turning off STP in Redundant Network

[MarkSimpson]

Hi guys, I am working on a project and would appreciate a couple of extra opinions...

• A customer has 3 sites (See diagram).
• Customer has several VLANs and swtches at each site (Not shown in the diagram).
• Sites A & B, B & C are connected by dedicated wireless antenne (Red dashed lines in the diagram).
• Intersite Links use a dedicated VLAN per antenna Link (VLAN 10 & 20).
• OSPF provides the routing between VLANs and between sites.

• Customer has a new Dedicated WAN connection via a provider, which is transparent network (Green cloud in the diagram).
• Ports connected to this new link are all in VLAN 40.

• Upon activating these new ports, MSTP (single instance) started blocking some of the links, VLAN 20 interface and VLAN 40 interface at Site A.
• Changing STP Mode to Rapid-PVST reconverged the network so that all intersite links were Forwarding.
• OSPF neighbors found on all VLANS.
• OSPF Costs have been configured so that the WAN is preferred over the wireless links.
• Testing shows OSPF neighbors and routing working as expected, simulating link failures shows alternative route being advertised as expected.
• Customer wishes to keep the wireless links as redundency incase the WAN link fails.

Now here is the question...

Given that the ports used for the intersite connections (wireless and WAN) are in thier own VLANs, can STP be disabled on these ports all together? as the traffic is only placed into these via OSPF.

Allthough the Network between the sites seems to work and is stable, enabling Rapid-PVST is effecting other areas of the network on Site C, which contains several other Switches configured in a MESH and Rapid-PVST resulting in undesired Blocked ports within the rest of the network.

I have tried moving VLAN 40 to MSTP instance 1 to no effect, still seen as a loop and therefore blocked.

Cheers

Mark

[MarkSimpson]

Any Opinons?