Service Manual

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 — inuences 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.
Enabling SNMP Traps for Root Elections and Topology Changes
To enable SNMP traps collectively, use this command.
Enable SNMP traps for RSTP, MSTP, and PVST+ collectively.
snmp-server enable traps xstp
Inuencing 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.
Example of the bridge-priority Command
A console message appears when a new root bridge has been assigned. The following example example shows the console message
after the bridge-priority command is used to make R2 the root bridge (shown in bold).
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Rapid Spanning Tree Protocol (RSTP)