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Enable Multiple Spanning Tree Globally
MSTP is not enabled by default. To enable MSTP globally, use the following commands.
When you enable MSTP, all physical, VLAN, and port-channel interfaces that are enabled and in Layer 2 mode are automatically
part of the MSTI 0.
Within an MSTI, only one path from any bridge to any other bridge is enabled.
Bridges block a redundant path by disabling one of the link ports.
1. Enter PROTOCOL MSTP mode.
CONFIGURATION mode
protocol spanning-tree mstp
2. Enable MSTP.
PROTOCOL MSTP mode
no disable
To verify that MSTP is enabled, use the show config command in PROTOCOL MSTP mode.
Dell(conf)#protocol spanning-tree mstp
Dell(config-mstp)#show config
!
protocol spanning-tree mstp
no disable
Dell#
Creating Multiple Spanning Tree Instances
To create multiple spanning tree instances, use the following command.
A single MSTI provides no more benefit than RSTP. To take full advantage of MSTP, create multiple MSTIs and map VLANs to
them.
Create an MSTI.
PROTOCOL MSTP mode
msti
Specify the keyword vlan then the VLANs that you want to participate in the MSTI.
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
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Multiple Spanning Tree Protocol (MSTP)