Chapter 19
| Spanning Tree Commands
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Example
Console(config)#interface ethernet 1/5
Console(config-if)#spanning-tree loopback-detection trap
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)
cost - Path cost for an interface. (Range: 0 for auto-configuration, 1-65535
for short path cost method
12
, 1-200,000,000 for long path cost method)
The recommended path cost range is listed in Table 96 on page 527.
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 8021w
standard exceeds 65,535, the default is set to 65,535. The default path costs are
listed in Table 97 on page 528.
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 1/5
Console(config-if)#spanning-tree mst 1 cost 50
Console(config-if)#
12. Use the spanning-tree pathcost method command to set the path cost method.
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