Dell M6220 User Configuration Manual page 658

2 Set the STP operational mode to MSTP.
console(config)#spanning-tree mode mst
3 Create MST instance 10 and associate it to VLAN 10.
console(config)#spanning-tree mst configuration
console(config-mst)#instance 10 add vlan 10
4 Create MST instances 20 and associate it to VLAN 20.
console(config-mst)#instance 20 add vlan 20
5 Change the region name so that all the bridges that want to be part of the
same region can form the region.
console(config-mst)#name dell
console(config-mst)#exit
6 (Switch A only) Configure Switch A to be the root bridge of the spanning
tree (CIST Regional Root) by configuring a higher root bridge priority.
console(config)#spanning-tree priority 8192
7 (Switch A only) Make Switch A the Regional Root for MSTI 1 by
configuring a higher priority for MST ID 10.
console(config)#spanning-tree mst 10 priority
12288
8 (Switch A only) Change the priority of MST ID 20 to ensure Switch C is
the Regional Root bridge for this MSTI.
console(config)#spanning-tree mst 20 priority
61440
console(config)#spanning-tree priority 8192
9 (Switch C only) Change the priority of port 1 to force it to be the root port
for MST 20.
console(config)#interface gi1/0/1
console(config-if-Gi1/0/1)#spanning-tree mst 20
port-priority 64
console(config-if-Gi1/0/1)#exit
658
Configuring the Spanning Tree Protocol