Deployment Guide

Example of the msti Command
Example of Viewing MSTP Port States
Dell(conf)#protocol spanning-tree mstp
Dell(conf-mstp)#msti 1 vlan 100
Dell(conf-mstp)#msti 2 vlan 200-300
Dell(conf-mstp)#show config
!
protocol spanning-tree mstp
no disable
MSTI 1 VLAN 100
MSTI 2 VLAN 200-300
All bridges in the MSTP region must have the same VLAN-to-instance mapping.
To view which instance a VLAN is mapped to, use the show spanning-tree mst vlan command from EXEC Privilege mode.
To view the forwarding/discarding state of the ports participating in an MSTI, use the show spanning-tree msti command from
EXEC Privilege mode.
Dell#show spanning-tree msti 1
MSTI 1 VLANs mapped 100
Root Identifier has priority 32768, Address 0001.e806.953e
Root Bridge hello time 2, max age 20, forward delay 15, max hops 19
Bridge Identifier has priority 32768, Address 0001.e80d.b6d6
Configured hello time 2, max age 20, forward delay 15, max hops 20
Current root has priority 32768, Address 0001.e806.953e
Number of topology changes 2, last change occured 1d2h ago on TenGig 1/21
Port 374 (TenGigabitEthernet 1/21) is root Forwarding
Port path cost 2000, Port priority 128, Port Identifier 128.374
Designated root has priority 32768, address 0001.e806.953e
Designated bridge has priority 32768, address 0001.e806.953e
Designated port id is 128.374, designated path cost 2000
Number of transitions to forwarding state 1
BPDU (MRecords): sent 93671, received 46843
The port isnot in the Edge port mode, bpdu filter is disabled
Port 384 (TenGigabitEthernet 1/31) is alternate Discarding
Port path cost 2000, Port priority 128, Port Identifier 128.384
Designated root has priority 32768, address 0001.e806.953e
Designated bridge has priority 32768, address 0001.e809.c24a
Designated port id is 128.384, designated path cost 2000
Number of transitions to forwarding state 1
BPDU (MRecords): sent 39291, received 7547
The port isnot in the Edge port mode, bpdu filter is disabled
Inuencing MSTP Root Selection
MSTP determines the root bridge, but you can assign one bridge a lower priority to increase the probability that it becomes the root bridge.
To change the bridge priority, use the following command.
• Assign a number as the bridge priority.
PROTOCOL MSTP mode
msti instance bridge-priority priority
A lower number increases the probability that the bridge becomes the root bridge.
The range is from 0 to 61440, in increments of 4096.
The default is 32768.
Example of Assigning and Verifying the Root Bridge Priority
By default, the simple conguration shown previously yields the same forwarding path for both MSTIs. The following example shows how
R3 is assigned bridge priority 0 for MSTI 2, which elects a dierent root bridge than MSTI 2.
Multiple Spanning Tree Protocol (MSTP)
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