Reference Guide

ethernet1/1/9 Disb 128.292 128 200000000 BLK 0 AUTO No
ethernet1/1/10 Disb 128.296 128 200000000 BLK
Root selection
MSTP determines the root bridge according to the lowest bridge ID. Assign a lower bridge priority to increase its likelihood of becoming the
root bridge.
• Assign a bridge priority number to a specic instance in CONFIGURATION mode (0 to 61440 in increments of 4096, default 32768).
Use a lower priority number to increase the likelihood of the bridge to become a root bridge.
spanning-tree mst instance-number priority priority
Assign root bridge priority
OS10(config)# spanning-tree mst 0
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 hardware
OS10 supports only one MST region. For a bridge to be in the same MST region as another, the three unique attributes (name, revision, and
VLAN-to-instance-mapping) must match. The default values for name and revision number match on all Dell hardware. If you have non-Dell
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 (default is the system MAC address).
• Revision — A 2-byte number (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 (up to 32 characters).
name name
Layer 2
193