PVST+ vs rapid-PVST+

dschlic1 · ‎07-19-2006

I have a network which consists of 28 2955C switches connected in a ring. The spanning tree works correctly if all of the switches are configured for PVST+. However if all of the switches are configured for rapid-PVST+ then multiple problems occur. Among them multiple roots, multiple switches disappearing from the network etc. Anyone know why?

globalnettech · ‎07-19-2006

Hello,

without knowing the exact details of your setup, make sure that all your VLANs are part of MST, since you cannot run PVST and MSTP at the same time. Also, try and set the root switch for your MST instance(s) manually, by using the 'spanning-tree mst instance-id root' command on the respective root switch.

HTH,

GNT

dschlic1 · ‎07-20-2006

I am not using MSTP or MST. There is only one VLAN on the network.

petr.novak · ‎07-26-2006

Problem might be network diameter, in this case 27 hops. IIRC rapid-PVST+ supports only 7hops. That will explain multiple roots - they just don't see each other.