340 | Multiple Spanning Tree Protocol (MSTP)
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Figure 19-3. Mapping VLANs to MSTI Instances
All bridges in the MSTP region must have the same VLAN-to-instance mapping. To view which instance
a VLAN is mapped, use the
show spanning-tree mst vlan <VLAN-ID> 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 (Figure 19-4).
Figure 19-4. Viewing MSTP Port States
Influence MSTP Root Selection
MSTP determines the root bridge, but you can assign one bridge a lower priority to increase the probability
of it becoming the root bridge.
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 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
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