[c-nsp] Quick spanning-tree and bridge-group question

[Sam Stickland]

Apologies I pasted some info where the path costs didn't total up to be 
the same. Here's the correct one.

The total path cost is 723 on every interface, the port priority on the 
Serial interface is higher.

The only logical conclusion appears to be that it's comparing the bridge 
IDs  before the port priority? Isn't this supposed to be the other way 
around?

Sam

R1#sh spanning-tree

 Bridge group 10 is executing the ieee compatible Spanning Tree protocol
  Bridge Identifier has priority 32768, address 0013.8050.b191
  Configured hello time 2, max age 20, forward delay 15
  Current root has priority 10, address 0019.aa7f.3480
  Root port is 28 (Serial0/0/0.10), cost of root path is 723
  Topology change flag not set, detected flag not set
  Number of topology changes 23 last change occurred 00:05:20 ago
          from FastEthernet0/1.161
  Times:  hold 1, topology change 35, notification 2
          hello 2, max age 20, forward delay 15
  Timers: hello 0, topology change 0, notification 0, aging 300

 Port 26 (FastEthernet0/1.161) of Bridge group 10 is blocking
   Port path cost 647, Port priority 128, Port Identifier 128.26.
   Designated root has priority 10, address 0019.aa7f.3480
   Designated bridge has priority 32929, address 0019.aab4.f700
   Designated port id is 112.3, designated path cost 76
   Timers: message age 5, forward delay 0, hold 0
   Number of transitions to forwarding state: 2
   BPDU: sent 863, received 5326

 Port 27 (FastEthernet0/1.162) of Bridge group 10 is blocking
   Port path cost 647, Port priority 128, Port Identifier 128.27.
   Designated root has priority 10, address 0019.aa7f.3480
   Designated bridge has priority 32930, address 0019.aab4.f700
   Designated port id is 112.3, designated path cost 76
   Timers: message age 6, forward delay 0, hold 0
   Number of transitions to forwarding state: 2
   BPDU: sent 862, received 5314

 Port 28 (Serial0/0/0.10) of Bridge group 10 is forwarding
   Port path cost 685, Port priority 144, Port Identifier 144.28.
   Designated root has priority 10, address 0019.aa7f.3480
   Designated bridge has priority 32768, address 0016.4699.0509
   Designated port id is 128.21, designated path cost 38
   Timers: message age 3, forward delay 0, hold 0
   Number of transitions to forwarding state: 3
   BPDU: sent 471, received 11176