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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 (TenGigabitEthernet 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
Influencing 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.
By default, the simple configuration 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 different root bridge than MSTI 2.
To view the bridge priority, use the show config command from PROTOCOL MSTP mode.
R3(conf-mstp)#msti 2 bridge-priority 0
1d2h51m: %RPM0-P:RP2 %SPANMGR-5-STP_ROOT_CHANGE: MSTP root changed for instance 2. My
Bridge ID: 0:0001.e809.c24a Old Root: 32768:0001.e806.953e New Root: 0:0001.e809.c24a
R3(conf-mstp)#show config
!
protocol spanning-tree mstp
no disable
MSTI 1 VLAN 100
MSTI 2 VLAN 200,300
MSTI 2 bridge-priority 0
Interoperate with Non-Dell Networking OS Bridges
Dell Networking OS supports only one MSTP region.
A region is a combination of three unique qualities:
● Name is a mnemonic string you assign to the region. The default region name on Dell Networking OS is null.
● Revision is a 2-byte number. The default revision number on Dell Networking OS is 0.
● VLAN-to-instance mapping is the placement of a VLAN in an MSTI.
For a bridge to be in the same MSTP region as another, all three of these qualities must match exactly. The default values for
name and revision match on all Dell Networking OS equipment. If you have non-Dell Networking OS equipment that participates
in MSTP, ensure these values match on all the equipment.
NOTE:
Some non-Dell Networking OS equipment may implement a non-null default region name. SFTOS, for example, uses
the Bridge ID, while others may use a MAC address.
Multiple Spanning Tree Protocol (MSTP) 537