Unanswered Question
May 18th, 2010
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Hi there,

My setup as below:

sw1 -----sw2

sw1 and sw2 are cisco 3560

sw1 root bridge for vlan 1-20
sw2 root bridge for vlan 20-40

sw1 pvst
sw2 mst

trunk conf
switchport trunk enca dot1q
sw mode trunk
sw trunk allowed vlan 1,3,6

sw2 mst config
instance 0 vlan 1,3,6
instance 1 vlan all exepct above

and when i enable the trunk i got error and link goes to blocking mode

%SPANTREE-2-PVSTSIM_FAIL: Blocking root port Gi0/24: Inconsitent inferior PVST BPDU received on VLAN 4, claiming root 24580:0022.55bb.1500

anything i am missing in my config to get this to work ?

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Giuseppe Larosa Tue, 05/18/2010 - 04:48
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Hello Marcin,

you cannot compare Rapid PVST with MST,

MST expects itself to be at the core of the network so it expects to be the root also on the link towards the RPVST device.

this is reasonable being MST more scalable.

try making SW2 MST instances to have better lower priority for all vlans

Hope to help



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