Bridge Priority in STP

Sir, we studied in class how STP works. Root switch is selected on the basis on lowest priority ID, but why the lowest priority switch is selected as root which will probably not have a block state port. so is priority id is just a number that we manipulate to decide root or it is used for some other thing in switch in some other way?

A STP root switch is elected in the following manner :

  1. The lowest priority switch wins the root switch election. By default, this value is 32768. This value can be changed in order to manipulate the root switch election. If the priority is a tie then

  2. The lowest MAC address switch wins the election.

The root switch will not have any blocked port.

i am clear about the election process. but my doubt is that when we say “priority” in general, more priority means more important. but in STP why is it opposite where less priority means more important because most important root switch is selected because of lowest priority. so the priority ID just some value or does it decides switch’s priority in some case?

Its a algorithm designed to choose lower priority.

The lower the number, the higher the priority

1 Like

You can think just like a Rank. Rank 1 is better than Rank 2.
The same logic goes for priority.