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STP election...when does it end?

I'm reading a book that talks about STP.

They give a diagram of 3 switches that are competing for root bridge status. My question is when does the election end exactly? The book talks about the process of exchanging BPDU's with each switch advertising themselves as root bridge. Then after they realize their buddy next to them has a better a bridge ID they advertise him as the root bridge.

So now we have all three switches realizing one of them is root bridge. When does the election end exactly? After they receive 5 consecutive BPDU's stating that SW1(switch 1) is root bridge? Are their timers? It never mentions exactly how it ends. It just says SW1 wins!!! How did they decide SW1 wins?

Reply to
ciscopimpenator
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I kept reading and found the answer. The ports are in a listening state by a default time of 15 seconds. For this amount of time they listen for BPDU's and forward them. Is this correct? By the time they transition to learning they should know who the root bridge is.

Reply to
ciscopimpenator

Yes that is correct. Listening and learning I believe.

There is also some setting cant remember right now but it can be set to adjust this by putting in the possible switch traversals into the equation.

Reply to
saintjmf

When a switch learn a BPDU with a root bridge and a priority more low that it stop sending BPDU's and only look new BPDU's.

Reply to
David Rosa

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