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the default is 2 seconds.
• Change the max-age parameter (the refresh interval for configuration information that is generated
by recomputing the spanning tree topology).
PROTOCOL SPANNING TREE mode
max-age seconds
The range is from 6 to 40.
The default is 20 seconds.
To view the current values for global parameters, use the show spanning-tree 0 command from
EXEC privilege mode. Refer to the second example in Enabling Spanning Tree Protocol Globally.
Modifying Interface STP Parameters
You can set the port cost and port priority values of interfaces in Layer 2 mode.
• Port cost — 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 default values are listed in Modifying Global Parameters.
To change the port cost or priority of an interface, use the following commands.
• Change the port cost of an interface.
INTERFACE mode
spanning-tree 0 cost cost
The range is from 0 to 65535.
The default values are listed in Modifying Global Parameters.
• Change the port priority of an interface.
INTERFACE mode
spanning-tree 0 priority priority-value
The range is from 0 to 15.
The default is 8.
To view the current values for interface parameters, use the show spanning-tree 0 command from
EXEC privilege mode. Refer to the second example in
Enabling Spanning Tree Protocol Globally.
Enabling PortFast
The PortFast feature enables interfaces to begin forwarding traffic approximately 30 seconds sooner.
Interfaces forward frames by default until they receive a BPDU that indicates that they should behave
otherwise; they do 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 you
Spanning Tree Protocol (STP)
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