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New Member

Finding the root bridge

What is the best way to track down the designated root bridge in a mult-switch environment??

Cisco Employee

Re: Finding the root bridge

Spanning tree is always per VLAN. If all your switches are CAT OS based, do a sh spantree and you should be able to track it from here. Look for the Designated root MAC address and the root port. If the switch itself is the root, the root port would be 1/0. The following page should help as well

Switch-15> (enable) sh spantree 1


spanning-tree enabled

spanning-tree type ieee

Designated Root 00-10-0d-b1-78-00 <<<-------

!-- MAC address of the root switch for VLAN 1.

Designated Root Priority 8192

Designated Root Cost 0

Designated Root Port 1/1 ,<<<<<<<<<----

New Member

Re: Finding the root bridge

A little more help here if you don't mind!

In your example

the Root Priority in 8192

Designated Root cost is 0

but the Designated root port is 1/1.

Does this mean this is not the Root bridge because the port is not 1/0??

Thanks for the clarification!!

Cisco Employee

Re: Finding the root bridge

I just tweaked the root port in the example to illustrate better:)(but I guess I did not). It was indeed the root brige in my example

New Member

Re: Finding the root bridge

Thanks for the clarification. I appreciate the help!!!!

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