Link to home
Create AccountLog in
Avatar of Michael Reeve
Michael ReeveFlag for United States of America

asked on

Spanning Tree Protocol

I have heard that Spanning Tree Protocol selects by default the oldest switch by manufacturers date for the Root Bridge. This is based on the lowest Bridge ID (combination of priority and MAC Address) placed on switches, since new switches will have a higher numbered MAC Address (I realize you can set the priority to change the root bridge). My question is, if the priority is the same on all switches (for example), will STP select the oldest switch strictly do to the fact it will have the lowest MAC Address and thus the lower Bridge ID? Does anyone have credible sources to make this claim or is this urban legend? Thanks very much in advance.
ASKER CERTIFIED SOLUTION
Avatar of Kenmcse1969
Kenmcse1969

Link to home
membership
Create an account to see this answer
Signing up is free. No credit card required.
Create Account
Avatar of Don Johnston
My question is, if the priority is the same on all switches (for example), will STP select the oldest switch strictly do to the fact it will have the lowest MAC Address and thus the lower Bridge ID?

This is correct. It's in the 802.1d spec. The age of the switch, however, is coincidental.  If a manufacture would assign MAC addresses to their switches starting with the last usable address in their OUI, then the opposite would be the case.
Avatar of Michael Reeve

ASKER

Exactly what I was looking for. Thank you!