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Command Line Interface
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4
Default Setting
auto
Command Mode
Interface Configuration (Ethernet, Port Channel)
Command Usage
• Specify a point-to-point link if the interface can only be connected to exactly
one other bridge, or a shared link if it can be connected to two or more bridges.
• When automatic detection is selected, the switch derives the link type from the
duplex mode. A full-duplex interface is considered a point-to-point link, while
a half-duplex interface is assumed to be on a shared link.
• RSTP only works on point-to-point links between two bridges. If you designate
a port as a shared link, RSTP is forbidden. Since MSTP is an extension of
RSTP, this same restriction applies.
Example
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.
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: 1-200,000,000)
The recommended range is -
• Ethernet: 200,000-20,000,000
• Fast Ethernet: 20,000-2,000,000
• Gigabit Ethernet: 2,000-200,000
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.
• Ethernet – half duplex: 2,000,000; full duplex: 1,000,000; trunk: 500,000
• Fast Ethernet – half duplex: 200,000; full duplex: 100,000; trunk: 50,000
• Gigabit Ethernet – full duplex: 10,000; trunk: 5,000
Console(config)#interface ethernet ethernet 1/5
Console(config-if)#spanning-tree link-type point-to-point