How stp BPDU communicate between cst,pvst and mst spanning tree mode.

Unanswered Question
Jul 24th, 2007


i am facing pvid inconsistancy and type inconsistancy problem in my network.

network connectivity


sw1 is cisco siwtch(spanning tree mode pvst+)

sw2 is extreme switch(spanning tree mode is CST,it is work on cst only)

Sw3 is cisco (spanning tree mode pvst+)

Thnaks & Reagrds


I have this problem too.
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chuckrenner Tue, 07/24/2007 - 14:12

According to your diagram, SW2 is in the middle, and the only switch attached to SW1 or SW3.

Based on this, PVST+ isn't doing anything for you. The only spanning-tree with more than one node will is the CST.

I also have to assume that you have 802.1Q trunks connecting these switches (since ISL is Cisco only).

So, based on your diagram, effectively, you really have only one spanning-tree, specifically the CST, because no PVST data should be passed through the extreme switch.

I have to assume that the diagram must be incomplete though, because there are no redundant links or layer 2 loops that even require STP of any kind.

Please share more details.

A more complete ASCII diagram of your port wiring for these switches would be nice.

Also, please give details of your trunking ports, (encapsulation, mode, etc.)

Finally, you may wish to post results from the following commands on each switch (I'm not sure what the extreme equivalents are):

* Show spanning-tree

* Show interface trunk

* Show vlan


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