We had a contract come in a propose a design for a new network topology at two of our sites and something he said did not sound right to me regarding spanning tree and the root bridge placement.
They current proposal is set a 3850 switch as our core layer 3 device. This switch will then link a number of our access switch around the building. Also connected off these devices there is a pair of Nexus devices which have our servers connected to. These nexus have two layer 2 connection to another set of nexus located in a different building hosting other servers (VPC).
I have had chance to look over their proposed config for the devices, and interestingly he has set the spanning tree priority to a lower value on the Nexus switches, instead of the 3850. This would mean that the nexus is more likely to become the root for spanning tree. There also a mix match of spanning tree (pvst and rapid-pvst) however I believe they compatible with each other).
If I understand spanning tree correctly the batter place to place it is in the “middle” device for that vlan i.e. our 3850. Is my understanding correct on this based on our topology? When questioning him, he said it should be on the nexus and did not give me a direct answer. Am not directly involved but just had a look over the plans.
Thanks
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