Please see preceding article here: http://www.experts-exchange.com/Networking/Operating_Systems/A_11209-Root-Bridge-Election.html
After Root Bridge has been elected, then what?.....
Let's start by defining a Root Port in lay man's terms
A Root Port is the switchport a switch chooses with the determination that it is the closest or fastest port to reaching the Root Bridge.
Notice "reaching the Root Bridge"
It is easy to confuse Root Ports as the ports on the Root Bridge. The Root Port is the port that leads to the Root Bridge.
From San Francisco, California, Interstate 5 Southbound leads to Los Angeles. You will not find any Highway inside Los Angeles that says "To Los Angeles". If you see any such sign around the area, then it means you are not in Los Angeles. The same I5 that takes you to L.A from S.F, takes you back to S.F. from L.A. in the reverse direction. The sign changes to "To San Francisco"
Long story short. You will never find a Root Port on a Root Bridge.
Any switch you see with a Root Port Label means it is not a Root Bridge.
I hope I made that clear enough without bugging you with repetition.
With that out of the way, there are several criteria the switch uses to determine which of its ports is most reliable path to the Root Bridge.
This also implies the following.
- There can only be 1 Root Port on a switch.
- All switches except the Root Bridge must each have a Root Port
Before I …