Configuring per-VLAN spanning tree

Syntax: 


spanning-tree vlan <vid-list> hello-time 1...10

Specifies the time in seconds between transmissions of BPDUs on the specified VLAN(s) when the switch is root for those VLAN(s).

Default: 2

Range: 1 - 10

Syntax: 


spanning-tree vlan <vid-list>forward-delay 4...30

Sets the time in seconds the switch waits before transitioning from listening to learning and from learning to forwarding states.

Default: 15

Range: 4 - 30

Syntax: 


spanning-tree vlan vid-listmaximum age 6...40

Sets the maximum age in seconds of received STP information before it is discarded for specified VLAN(s).

Default: 20

Range: 6 - 40

NOTE:
Maximum age must be within the following bounds:

  • greater than or equal to 2x (hello-time +1)

  • less than or equal to 2x (forward-delay - 1)

Syntax: 


spanning-tree vlan vid-list priority 0...15

Sets the switch (bridge) priority for the designated VLAN. The switch compares this priority with the priorities of other switches on the same VLAN to determine the RPVST+ root switch for the VLAN. The lower the priority value, the higher the priority. The switch with the lowest Bridge Identifier on the VLAN is elected as the RPVST+ root switch for that VLAN.

The Bridge Identifier is composed of a configurable Priority (2 bytes) and the switch’s MAC address (6 bytes). You can change the Priority provides flexibility for determining which switch on the VLAN will be the root for RPVST+, regardless of its MAC address.

The priority range for an RPVST+ switch is 0-61440. However, this command specifies the priority as a multiplier (0 - 15) of 4096. That is, when you specify a priority multiplier value of 0 - 15, the actual priority assigned to the switch is: (priority-multiplier) x 4096.

For example, if you configure “2” as the priority-multiplier on a given RPVST+ switch, then the Switch Priority setting for the specified VLAN is 8,192.

NOTE:

If multiple switches on the same VLAN have the same priority setting, then the switch with the lowest MAC address becomes the root switch for that VLAN.

Syntax: 

spanning-tree vlan vid-list root {primary | secondary}
no spanning-tree vlan vid-list root {primary | secondary}

Specifies the switch as the primary or secondary root bridge for the specified VLAN(s). Otherwise, by default, the root bridge for each VLAN will be determined by the lowest MAC address in that topology.

The no form of the command returns the determination of root to the lowest MAC address criterion.