Root path cost question....

[jimmysands73_2]

What is the command to see the culmlative cost to a root bridge?

I thought the info would be

Switch#sh span int fa0/11 det

Port 11 (FastEthernet0/11) of VLAN0001 is designated forwarding

   Port path cost 19, Port priority 128, Port Identifier 128.11.

   Designated root has priority 32769, address 0007.8432.dd00

   Designated bridge has priority 32769, address 000b.fd67.6500

   Designated port id is 128.11, designated path cost 19

   Timers: message age 0, forward delay 0, hold 0

   Number of transitions to forwarding state: 1

   Link type is point-to-point by default

   BPDU: sent 68, received 1

Switch#

But it is not.  My root bridge is a path cost of 38 away, not 19.

Thank you

[jimmysands73_2]

Attached is the topology

RB is ALS2, and the command I pasted was from DLS2

[jimmysands73_2]

And I had the question recently of

Are BPDUs propagated w/out trunk link?

I would say yes, if you have a flat network, and everything is on VLAN 1. Is this wrong?

[Jon Marshall · Accepted solution]

Can you post the output of "sh spanning-tree vlan 1" from DSL2 ?

The path to root is the cost from the root port which i would have thought would be fa0/7 or fa0/8 from DSL2 to ALS2. 

Yes BPDU's are sent on an access link port by default because there is nothing to stop you connecting up 2 switches using ports in only one vlan rather than a trunk link.

Jon

[jimmysands73_2]

Thank you, will do.  Will log into lab tomorrow and post then.

[jimmysands73_2]

Turns out I was not using the correct command,

Its below.  Note this was just a lab, so the numbers might not jive with my previous post.

ALS2#sh spa vla 1 de

VLAN0001 is executing the ieee compatible Spanning Tree protocol

  Bridge Identifier has priority 32768, sysid 1, address 0009.b79f.7d80

  Configured hello time 2, max age 20, forward delay 15

  Current root has priority 24577, address 000f.2303.2d80

  Root port is 11 (FastEthernet0/11), cost of root path is 38

  Topology change flag set, detected flag not set

  Number of topology changes 15 last change occurred 00:00:54 ago

          from FastEthernet0/8

  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 15