Does Spanning Tree priority matter if there are no redundant paths?

andyalder
andyalder used Ask the Experts™
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There is one central gigabit switch with 4 * 100Mb switches connected to it using fast etherchannel.  There's also another gigabit switch connected to the central switch. There are no redundant paths unless you count two cables going from one switch to another bundled using fast etherchannel. Similarly the servers are all connected to the central switch with a couple of cables using LACP or fast etherchannel.

The only connections between the switches all go to the central switch, the edge switches are not interconnected.

I've just been told by the customer I set this up for that it may be very slow because all traffic may go to one of the slower "edge" switches and back again just because that may have the highest priority as far as spanning tree is concerned. That doesn't make much sense to me.

So question is did I set it up wrong by not fixing priorities or doesn't it matter if there are no alternate paths?
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Spanning tree shouldn't be an issue in your no loop topology unless something is causing it the change topology often. But you should prioritize your bridge priority setting so the core switch is the root bridge.
Don JohnstonInstructor
Top Expert 2015
Commented:
>I've just been told by the customer I set this up for that it may be very slow because all traffic may go to one of the slower "edge" switches and back again just because that may have the highest priority as far as spanning tree is concerned.

Nope. No chance of that given the topology you describe.

>So question is did I set it up wrong by not fixing priorities or doesn't it matter if there are no alternate paths?

Not really. Best practice would be to configure the central switch with the lower priority but since you don't have any redundant links, it won't make any difference.

Just remember that if something happens with any of the etherchannel links, those individual ethernet links will become redundant links and spanning tree then becomes an issue.
Top Expert 2014

Author

Commented:
Thanks for two confirmations so far that I didn't goof. will close in morning.

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