Configuring Root Bridge Primary and Secondary on a Switch Stack

[tonymitchell]

Hi, Consider a small LAN using a collapsed core design with two Catalyst 3650 switches in a stack as the core/distribution layer. There are several 2960X switches with cross-stack EtherChannels to the 3650's. After enabling Rapid-PVST, best practice would be to configure the root bridge. The question is, would it be sufficient to configure the stack to be the Root Primary and not configure a secondary, based on a failure of the stack master switch would elect the slave to become the stack master and effectively become the root bridge?

Thanks

Tony

[Jon Marshall · Accepted solution]

Tony

You shouldn't need to configure a secondary root on the same switch stack because there is only one configuration file that is used for all stack members.

So, as you say, if the current stack master fails then a new one is elected and it will use the existing running configuration which has the STP root set.

Jon

[tonymitchell]

Thanks Jon.... just wanted to sanity check that, as I couldn't find a configuration example anywhere!

Kind Regards

Tony

[Joseph W. Doherty]

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Posting

BTW, don't know if issue also applies to 3650 stacks, but on 3750 stacks, if stack master fails, I believe your port channels will reset because, by default, stack's MAC changes.  However (again at least for 3750s), the stack can be configured to retain the original master MAC.