If a switch is configured with the following:
SwitchB(config)# spanning-tree extended system-id
SwitchB(config)# spanning-tree vlan 5 root primary
If SwitchA is the root bridge with a priority of 4200, i suppose SwitchB has no chance of becoming the new root.(As the new priority of SwB must be 2400-2096=104, but since the priority is in multiples of 4096 so the priority of swB infact remains unchanged)
What is the lower threshold priority for avoiding this situation? I mean what is the minimum root priority value of SwitchA so that SwitchB can take over as the new root bridge with the configuration above? Should it be 8192?
PS: I have no equipment or simulations to test the situation for the time being.