696 | Multiple Spanning Tree Protocol (MSTP)
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Create Multiple Spanning Tree Instances
A single MSTI provides no more benefit than RSTP. To take full advantage of MSTP you must create
multiple MSTIs and map VLANs to them.
Create an MSTI using the command
msti from PROTOCOL MSTP mode. Specify the keyword vlan
followed by the VLANs that you want to participate in the MSTI, as shown in Figure 32-3.
Figure 32-3. Mapping VLANs to MSTI Instances
All bridges in the MSTP region must have the same VLAN-to-instance mapping. View to which instance a
VLAN is mapped using the command
show spanning-tree mst vlan from EXEC Privilege mode, as shown in
Figure 32-6.
View the forwarding/discarding state of the ports participating in an MSTI using the command
show
spanning-tree msti
from EXEC Privilege mode, as shown in Figure 32-4.
Figure 32-4. Viewing MSTP Port States
FTOS(conf)#protocol spanning-tree mstp
FTOS(conf-mstp)#msti 1 vlan 100
FTOS(conf-mstp)#msti 2 vlan 200-300
FTOS(conf-mstp)#show config
!
protocol spanning-tree mstp
no disable
MSTI 1 VLAN 100
MSTI 2 VLAN 200-300
FTOS#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 Gi 1/21
Port 374 (GigabitEthernet 1/21) is root Forwarding
Port path cost 20000, 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 20000
Number of transitions to forwarding state 1
BPDU (MRecords): sent 93671, received 46843
The port is not in the Edge port mode
Port 384 (GigabitEthernet 1/31) is alternate Discarding
Port path cost 20000, 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 20000
Number of transitions to forwarding state 1
BPDU (MRecords): sent 39291, received 7547
The port is not in the Edge port mode
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