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I am still understanding a bit about this priority for spanning-tree on VLANs. I have a SWITCH A that is the root of a VLAN. It trunks through SWITCH B with no ports on that vlan. SWITCH B trunks to SWITCH C which does have access on that vlan.
If SWITCH A is priority 0. What is SWITCH B and SWITCH C?
Is SWITCH C 4096? If so is SWITCH B 8192?
STP and RSTP are entirely VLAN agnostic. Any bridge priority is the one you have configured on that bridge - the default is 32768 (8). Which VLANs and port memberships you configure is of no relevance.
The same is true for MSTP unless you configure multiple instances (and possibly regions). Each instance (in a region) allows a participating bridge to set different bridge and port priorities.
Cisco's (R)PVST(+) is a somewhat different beast in that it generally creates an independent spanning tree for each VLAN. The bridge and port priorities work the same however.
In no case does one bridge's priority change any of the others. The only bridge priority that is really relevant is the lowest value; the others become only relevant when the root bridge is removed from the network and another one needs to be elected.
