I have an interesting STP problem. I am a little fuzzy on exactly how MST is supposed to work with one region configured. I have one region with instances 0 an 1 set as the root on my core 6513. I have 2 distribution switches each connected to the core and then an access switch dual homed to each distribution switch. I assumed that each distribution switch would set the uplink to to the core as the root port, but it seems one of them is not behaving the way i expected. Why would it choose a port that has a higher root path cost as root port? I'm totally confused on this. See the below from the distribution switch in question. Since I have one region why is my core 6513 not the regional root as well? Any help is greatly appreciated.
##### MST0 vlans mapped: none
Bridge address 0026.cb68.da40 priority 32768 (32768 sysid 0)
Root address f0f7.55be.bac0 priority 24576 (24576 sysid 0)
port Gi2/2 path cost 2000
Regional Root address 0026.cb68.da00 priority 32768 (32768 sysid 0)
internal cost 40000 rem hops 18
Operational hello time 2 , forward delay 15, max age 20, txholdcount 6
Configured hello time 2 , forward delay 15, max age 20, max hops 20
Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Te1/1 Altn BLK 2000 128.1 P2p Bound(RSTP)
Gi2/1 Altn BLK 20000 128.65 P2p
Gi2/2 Root FWD 20000 128.66 P2p
