Thanks for the reply. I'm not sure I fully understand your response. Are you stating that as long as all access switches are "physically" connected to the core or "logically". In the case of this network, each building has a switch that distributes out to access, but all paths lead back to the HP core ultimately. I can't comment on Cisco network yet, still waiting for that informaiton. Handoffs would need to be made in several network closets throughout multiple buildings between the Cisco and HP networks. So does this idea work in this case. Does disabling spanning tree on interfaces cause them to ignore BPDUs from either network?
What about creating a new MSTP instance, set a high priority, and add necessary VLANs? Would that shield the rest of the network? I'm trying to brush up on spanning tree knowledge as I've never encountered different vendor network that I didn't control. Sorry if this is elementary questions. Thanks for the help!