User Guide    334
Configuring Spanning Tree MSTP Configurations
Interface       Prio    Cost        Role        Status       LAG
-----------     ------   ------      --------    ---------    -------
Gi1/0/3           144    200        N/A          LnkDwn    N/A
Switch(config-if)#end
Switch#copy running-config startup-config
3.2.3  Configuring Global MSTP Parameters
Follow these steps to configure the global MSTP parameters of the switch:
Step 1 configure
Enter global configuration mode.
Step 2 spanning-tree priority 
pri
Configure the priority of the switch for comparison in CIST.
pri
: Specify the priority for the switch. The valid value is from 0 to 61440, which are divisible 
by 4096. The priority is a parameter used to determine the root bridge for spanning tree. The 
switch with the lower value has the higher priority.
In STP/RSTP, the value is the priority of the switch in spanning tree. The switch with the highest 
priority will be elected as the root bridge.
In MSTP, the value is the priority of the switch in CIST. The switch with the higher priority will be 
elected as the root bridge in CIST.
Step 3 spanning-tree timer {[ forward-time 
forward-time
 ] [ hello-time 
hello-time
 ] [ max-age 
max-
age
 ]}
(Optional) Configure the Forward Delay, Hello Time and Max Age.
forward-time: 
Specify the value of Forward Delay. It is the interval between the port state 
transition from listening to learning. The valid values are from 4 to 30 in seconds, and the default 
value is 15. Forward Delay is used to prevent the network from causing temporary loops during 
the regeneration of spanning tree. The interval between the port state transition from learning 
to forwarding is also the Forward Delay.
hello-time: 
Specify the value of Hello Time. It is the interval between BPDUs’ sending. The 
valid values are from 1 to 10 in seconds, and the default value is 2. The root bridge sends 
configuration BPDUs at an interval of Hello Time. It works with the MAX Age to test the link 
failures and maintain the spanning tree.
max-age: 
Specify the value of Max Age. It is the maximum time that the switch can wait without 
receiving a BPDU before attempting to regenerate a new spanning tree. The valid values are 
from 6 to 40 in seconds, and the default value is 20.
Step 4 spanning-tree hold-count 
value
(Optional) Specify the maximum number of BPDU that can be sent in a second.
value:
 Specify the maximum number of BPDU packets that can be sent in a second. The valid 
values are from 1 to 20 pps, and the default value is 5.
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