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PVST-MSTP root bridge problem

Hi, we have a problem on the boundary of MST and PVST.

A 2950 is the boundary switch. Root for all VLANs is inside MST region with priority 24576.We have instance 1 and 2 where all vlans between 1 and 1000 belong to. On 2950 we have only defined few VLANS belonging to region 2. When we connect a 3500XL via dot1q trunk, this switch also claims to be root.We get root inconsistent msg because of root guard.When we remove root guard on 2950 for this trunk, the 3500Xl still claims to be the root (for some VLANs?). But net does not become stable.

My question is if VLAN 1 has to belong to IST region 0?

Is there any problem due to extended system ID we use inside MST?

Is there a problem with MST/PVST via dot1q trunk?

Any other ideas are welcome.Regards Guenther

New Member

Re: PVST-MSTP root bridge problem

Problem solved. We had to set lower prority also for IST (mst 0)on root bridge.

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