Dell PowerConnect 8100 CLI Reference Guide - Page 735

Default Configuration VLANs are mapped to the common and internal spanning tree (CIST) instance (instance 0). Command Mode MST mode User Guidelines Before mapping VLANs to an instance use the spanning-tree mst enable command to enable the instance. All VLANs that are not explicitly mapped to an MST instance are mapped to the common and internal spanning tree (CIST) instance (instance 0) and cannot be unmapped from the CIST. For two or more switches to be in the same MST region, they must have the same VLAN mapping, the same configuration revision number, and the same name. PowerConnect MSTP supports mapping of VLANs to MST instances, even though the underlying VLAN may not be defined on the switch. Traffic received on VLANs not defined on the port received is dropped. Example The following example maps the entire range of VLANs to MST instances (MST instance 0 is mapped to VLAN 1 by default). Additionally, two 10G ports have some, but not all, of the VLANs mapped to MST instances. console(config)#spanning-tree mode mst console(config)#spanning-tree mst 1 priority 8192 console(config)#spanning-tree mst 2 priority 28672 console(config)#spanning-tree mst configuration console(config-mst)#instance 1 add vlan 2-199 console(config-mst)#instance 1 add vlan 350 console(config-mst)#instance 1 add vlan 400-449 console(config-mst)#instance 1 add vlan 500-1999 console(config-mst)#instance 1 add vlan 2200-2499 console(config-mst)#instance 1 add vlan 2600-2799 console(config-mst)#instance 1 add vlan 3000-4093 console(config-mst)#instance 2 add vlan 200-349 console(config-mst)#instance 2 add vlan 351-399 Spanning Tree Commands 735