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33
Spanning Tree Commands
spanning-tree mst cost
This command configures the path cost on a spanning instance in the Multiple
Spanning Tree. Use the no form to restore the default auto-configuration mode.
Syntax
spanning-tree mst instance_id cost cost
no spanning-tree mst instance_id cost
• instance_id - Instance identifier of the spanning tree.
(Range: 0-4094, no leading zeroes)
• cost - Path cost for an interface. (Range: 0 for auto-configuration, 1-65535
for short path cost method
The recommended path cost range is listed in Table 33-2 on page 33-12.
Default Setting
By default, the system automatically detects the speed and duplex mode
used on each port, and configures the path cost according to the values
shown below. Path cost "0" is used to indicate auto-configuration mode.
When the short path cost method is selected and the default path cost
recommended by the IEEE 8021D-2004 standard exceeds 65,535, the
default is set to 65,535. The default path costs are listed in Table 33-3 on
page 33-12.
Command Mode
Interface Configuration (Ethernet, Port Channel)
Command Usage
• Each spanning-tree instance is associated with a unique set of VLAN IDs.
• This command is used by the multiple spanning-tree algorithm to determine
the best path between devices. Therefore, lower values should be assigned
to interfaces attached to faster media, and higher values assigned to
interfaces with slower media.
• Use the no spanning-tree mst cost command to specify auto-configuration
mode.
• Path cost takes precedence over interface priority.
Example
Console(config)#interface ethernet ethernet 1/5
Console(config-if)#spanning-tree mst 1 cost 50
Console(config-if)#
Related Commands
spanning-tree mst port-priority (33-17)
29. Use the spanning-tree pathcost method command on page 33-6 to set the path cost method.
33-16
29
, 1-200,000,000 for long path cost method)
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