21. CISCO CML STP Priority 4096 vs root primary
Default Priority is 32768
Root Primary Priority is 24576 = 32768 - 4096 - 4096
Root Secondary Priority is 28672 = 32768 - 4096
spanning-tree vlan 1-4094 root primary
= spanning-tree vlan 1-4094 priority 24576(translated)
SW3 Priority 16384
When you configure spanning-tree vlan 1-4094 root primary
it check currunt root bridge priority then, minus 4096 of currunt root bridge priority
If the root bridge priority is already configured as 4096, the "root primary "commands will be ignored
% Failed to make the bridge root for vlan 1,50
% It may be possible to make the bridge root by setting the priority
% for some (or all) of these instances to zero.