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Spanning tree vlan root primary on B-series, C-series, K-series, N-series, S-series

Spanning tree vlan root primary on B-series, C-series, K-series, N-series, S-series

New Contributor
Hi, maybe is a silly or complex question but ...

Recently we discovered an issue on our data center network where a vlan suffered connection loss; as we found it was all caused by an old switch that was automatically elected as root primary for the affected vlan. We proceded to configure our core chassis to be primary root at the mentioned vlan and problem was solved. the core switch is non enterasys/extreme and the old switch was a very old enterasys switch. probably the old switch dont had the ram/cpu/forwarding capacity to be a root on any vlan !!!

Now, the thing is that i want to make sure that all of my remote sites ( that are almost completely enterasys/extreme based ) had the appropiate settings in order to ensure that the most capable enterasys/extreme switch onsite is primary root and not had the issue of a slow switch performing as primary root.

how can it be done ? thanks in advance....

Extreme Employee
Hi Franciscoo,

Out of interest , are all the old edge switches on default priority settings ? if they are then as long as you have set the priority on the root bridge to for example ,zero then there is no way that you will have an issue with root bridge election. If someone has manually changed the priorities then there is a chance that they could be same as root bridge and then it will be lowest mac , which is the older device normally that becomes root. Really checking the priority configurations are consistent is the only way to be sure this doesn't happen.

There is also a feature called restricted role which may help you but this is not supported on all the listed products. See the information below:

Hope this helps
Best Regards

Thanks Glyn...

Contributor II
Hi Francisco,

you need to set the STP priorities of the switches you want to have as root (both primary and secondary).

You should always use compatible STP version. Per-VLAN spanning tree implementations available from different vendors are non-standard and only partially compatible with other spanning tree implementations, both standard and non-standard. A good choice is MST, which is standard, broadly supported across vendors, and downwards compatible with both the older standards, original and rapid spanning tree protocols.


Thanks for your insight