Spanning Tree MST and 3750

Unanswered Question
May 12th, 2009
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We have a network with c6500 as distribution and c3750E stacks as access.

We use MST for failover/loop prevention.

I have seen a couple of times that when I connect a new 3750 and change spanning-tree mode to "mst" - the status of root port becomes "p2p (bound pvst)"

When the redundant uplink is connected we get a l2 loop. Seems like I have to boot the 3750 once after changing to "mst". After boot it gets correct status "p2p".

Any idea why?

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Giuseppe Larosa Wed, 05/13/2009 - 12:36
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Hello Jorgen,

you have already found a workaround and you are not going to change STP mode everyday.

It can be a software issue related to the specific IOS image you are using, or simply it requires more time or some event to trigger the new MST instances to start.



>> when I connect a new 3750

do you mean you are adding a new stack or a new switch to an existing stack ?

Hope to help


jorgensor Wed, 05/13/2009 - 23:18
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It's when we add a new stack to the network.

If this is a bug it must be prettu critical ... The whole network went down for us because of this.


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