Reference Guide

Modifying the Interface Parameters
You can adjust two interface parameters to increase or decrease the probability that a port becomes a
forwarding port.
• Port cost is a value that is based on the interface type. The greater the port cost, the less likely the
port is selected to be a forwarding port.
• Port priority influences the likelihood that a port is selected to be a forwarding port in case that
several ports have the same port cost.
The following lists the default values for port cost by interface.
Table 32. Default Values for Port Costs by Interface
Port Cost Default Value
100-Mb/s Ethernet interfaces 200000
1-Gigabit Ethernet interfaces 20000
10-Gigabit Ethernet interfaces 2000
Port Channel with 100 Mb/s Ethernet interfaces 180000
Port Channel with 1-Gigabit Ethernet interfaces 18000
Port Channel with 10-Gigabit Ethernet interfaces 1800
To change the port cost or priority of an interface, use the following commands.
1. Change the port cost of an interface.
INTERFACE mode
spanning-tree msti number cost cost
The range is from 0 to 200000.
For the default, refer to the default values shown in the table..
2. Change the port priority of an interface.
INTERFACE mode
spanning-tree msti number priority priority
The range is from 0 to 240, in increments of 16.
The default is 128.
To view the current values for these interface parameters, use the show config command from
INTERFACE mode.
Configuring an EdgePort
The EdgePort feature enables interfaces to begin forwarding traffic approximately 30 seconds sooner.
In this mode, an interface forwards frames by default until it receives a BPDU that indicates that it should
behave otherwise; it does not go through the Learning and Listening states. The bpduguard shutdown-
on-violation option causes the interface hardware to be shut down when it receives a BPDU. When
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Multiple Spanning Tree Protocol (MSTP)