Users Guide

You can set the priority value to 0 to force a switch to become the root switch. Value 0 is the highest priority.
● Assign a bridge priority number to a specific instance in CONFIGURATION mode, from 0 to 61440 in increments of 4096,
default 32768.
spanning-tree mst instance-number priority priority
Assign root bridge priority
OS10(config)# spanning-tree mst 0 priority 32768
Verify root bridge priority
OS10# show spanning-tree active
Spanning tree enabled protocol msti with force-version mst
MSTI 0 VLANs mapped 1,31-4093
Executing IEEE compatible Spanning Tree Protocol
Root ID Priority 32768, Address 3417.4455.667f
Root Bridge hello time 2, max age 20, forward delay 15, max hops 20
Bridge ID Priority 32768, Address 90b1.1cf4.a523
Configured hello time 2, max age 20, forward delay 15, max hops 20
CIST regional root ID Priority 32768, Address 90b1.1cf4.a523
CIST external path cost 500
Interface Designated
Name PortID Prio Cost Sts Cost Bridge ID PortID
---------------------------------------------------------------------------
ethernet1/1/5 128.276 128 500 FWD 0 32768 3417.4455.667f 128.146
ethernet1/1/6 128.280 128 500 BLK 0 32768 3417.4455.667f 128.150
Interface
Name Role PortID Prio Cost Sts Cost Link-type Edge
--------------------------------------------------------------
ethernet1/1/5 Root 128.276 128 500 FWD 0 AUTO No
ethernet1/1/6 Altr 128.280 128 500 BLK 0 AUTO No
Non-Dell EMC hardware
OS10 supports only one MST region. For a bridge to be in the same MST region as another, the following attributes must match
the unique name, revision, and VLAN mapping. The default value for name is system mac. In case of Dell EMC, the user has to
manually configure an unique name in all the nodes to be in a single region. If you have non-Dell EMC hardware that participates
in MST, ensure these values match on all devices.
A region is a combination of three unique attributes:
● Name — A mnemonic string you assign to the region. The default is the system MAC address.
● Revision — A 2-byte number. The default is 0.
● VLAN-to-instance mapping — Placement of a VLAN in an MSTI.
Region name or revision
You can change the MSTP region name or revision.
● Change the region name in MULTIPLE-SPANNING-TREE mode. A maximum of 32 characters.
name name
● Change the region revision number in MULTIPLE-SPANNING-TREE mode, from 0 to 65535, default 0.
revision number
Configure and verify region name
OS10(conf-mstp)# name my-mstp-region
OS10(conf-mstp)# do show spanning-tree mst config
MST region name: my-mstp-region
Revision: 0
MSTI VID
538
Layer 2