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I have four Switches that are interconnected with each other, witch form a loop as shown in this network diagram Network Diagram

The switch 1 is the root bridge and is connected to the primary edge router. The switch 2 is the failover root bridge and is connected to the secondary edge router. The two switches are interconnected with a 10 Gb/s module. The connections to the other switches are all 1 Gb/s (either with SFP and fibre or ethernet cable).

The priorities are set as shown in the diagram.

Now I'd like that path between switch 3 and switch 4 to be blocked. So I'd like to know if with my current configuration STP blocks the path between switch 3 and switch 4automatically, as it's the path with the heighest cost leading to the root bridge or should I configure it specifically? How would one do such a configuration?

The switches are configured with mstp.

Kevin K.
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Skanderbeg
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  • Have you tried logging on the switches and look at the diagnostic output for spanning tree? I can't remember the HP syntax from the top of my head, but I'm going to guess "show span" – pauska Jul 17 '18 at 10:25

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Essentially, SW2's STP priority doesn't matter as it's only used for root election.

Since SW4's path costs are 1G+1G across SW3 but 1G+10G across SW2, the latter is set as root path and the former is blocked - it'll automatically do what you'd like. The better 10G link cost tends to attract the active links in the tree.

To achieve the same with an equal path setup you'd need to lower the interface priority to set the spanning tree as desired.

Zac67
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