Reference Guide

The range is from 1 to 10.
The default is 2 seconds.
● Change the max-age parameter.
PROTOCOL SPANNING TREE RSTP 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 rstp command from EXEC privilege mode.
Enabling SNMP Traps for Root Elections and Topology Changes
To enable SNMP traps, use the following command.
● Enable SNMP traps for RSTP, MSTP, and PVST+ collectively.
snmp-server enable traps xstp
Modifying Interface Parameters
On interfaces in Layer 2 mode, you can set the port cost and port priority values.
● Port cost — a value that is based on the interface type. The previous table lists the default values. 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.
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 rstp cost cost
The range is from 0 to 65535.
The default is listed in the previous table.
● Change the port priority of an interface.
INTERFACE mode
spanning-tree rstp priority priority-value
The range is from 0 to 15.
The default is 128.
To view the current values for interface parameters, use the show spanning-tree rstp command from EXEC privilege
mode.
Influencing RSTP Root Selection
RSTP determines the root bridge, but you can assign one bridge a lower priority to increase the likelihood that it is selected as
the root bridge.
To change the bridge priority, use the following command.
● Assign a number as the bridge priority or designate it as the primary or secondary root.
PROTOCOL SPANNING TREE RSTP mode
bridge-priority priority-value
○ priority-value The range is from 0 to 65535. The lower the number assigned, the more likely this bridge becomes
the root bridge.
The default is 32768. Entries must be multiples of 4096.
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Rapid Spanning Tree Protocol (RSTP)