14.
Multiple Spanning Tree Protocol (MSTP)
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Argument Description
instance-id
The MST instance ID. The range is 0 to 15.
priority
<priority>
Determines the likelihood that the switch will be chosen as the root switch.
The range is 0 (highest likelihood) to 61440 (lowest likelihood) at increments of
4096. The default priority value is 32768.
The valid priority values are 0, 4096, 8192, 12288, 16384, 20480, 24576, 28672,
32768, 36864, 40960, 45056, 49152, 53248, 57344, and 61440. All other values
are rejected.
Configuring the MSTP Interface Parameters
Table 14-6 lists the MSTP interface configuration commands.
Table 14-6 MSTP Interface Configuration Commands
C o m m a n d D e s c r i p t i o n
mstp port priority
Sets the MSTP port priority.
mstp path-cost
Sets the path cost of the MSTP port.
mstp edge-port
Sets the edge port.
mstp link-type
Specifies the type of the link.
mstp default
Sets the default MSTP port.
mstp detect-protocols
Forces the port to work by the Rapid Spanning Tree Protocol
(RSTP) and not by the Spanning Tree Protocol (STP).
mstp cisco-compliant
Enables the port to work with Cisco-compliant devices.
Setting the MSTP Port Priority
The
mstp port priority
command, in Interface Configuration mode, defines the MST port
priority. The
no
form of this command returns the interface to its default settings.
By default, the spanning tree port priority is 128.
If a loop occurs, the MSTP uses the port priority when selecting an interface to put into the
forwarding state. You can assign higher priority values (lower numerical values) to interfaces
to be selected first and lower priority values (higher numerical values) to interfaces to be
selected last. If all interfaces have the same priority value, the MSTP puts the interface with
the lowest interface number in the forwarding state and blocks the other interfaces.
Command Syntax
device-name
(config-if
UU/SS/PP
)#
mstp
<
instance-id
>
port-priority
<
priority
>
device-name
(config-if
UU/SS/PP
)#
no mstp
<
instance-id
>
port-priority
Argument Description
instance-id
The MST instance ID. The range is <0-15>.