Article Number: 000120251
Topics Covered
Configure Per-VLAN Spanning Tree Plus
Configure PVST+ is a four-step process.
Enabling PVST+
Command Line Example
Command |
Purpose |
Console# configure |
Enters configuration level on the switch. |
Console(config)# protocol spanning-tree pvst |
Set the specific spanning-tree protocol. |
Console(conf-pvst)#no disable |
Enable spanning-tree globally. |
Configuring EdgePort
It is recommended to configure any edge ports, ports that go to end devices such as printers, phones, servers, workstations, to be set up as Edge-Port. A port in Edge-Port will move directly to forwarding state when the link comes up without waiting for the forward-time delay.
Command Line Example
Command |
Purpose |
console# configure |
Enter configuration level on the switch. |
console(config)# interface te 0/1 |
Enter the desired physical port interface. |
console (conf-if-te-0/1)# spanning-tree pvst edge-port |
Enables Edge-port on the interface. |
console (conf-if-te-0/1)# no spanning-tree pvst edge-port |
Disables Edge-port on the interface. |
Influencing PVST+ Root Selection
The bridge with the lowest bridge value for bridge priority is elected root. Because all bridges use the default priority (until configured otherwise), the lowest MAC address is used as a tie-breaker. To increase the likelihood that a bridge is selected as the STP root, assign bridges a low non-default value for bridge priority.
The following per-VLAN spanning tree illustration changes the bridge priority of each bridge so that a different forwarding topology is generated for each VLAN. This behavior demonstrates how you can use PVST+ to achieve load balancing.
Figure 1 - Load Balancing with PVST+
To assign a bridge priority, use the following command.
console(conf-pvst)# vlan X bridge-priority <0-61440>
The range is from 0-61440.
The default is 32768.
Command Line Example
Command |
Purpose |
Console# configure |
Enters configuration level on the switch. |
Console(config)# protocol spanning-tree pvst |
Set the specific spanning-tree protocol. |
Console(conf-pvst)# vlan 100 bridge-priority 4096 |
Set VLAN spanning-tree priority. Range <0 – 61440>. In increments of 4096. |
Verification Commands
Command |
Purpose |
Console# show spanning-tree pvst vlan 100 |
View VLAN level spanning tree settings. |
Console# show spanning-tree pvst |
View global spanning-tree settings. |
Force10 S60-44T
18 Mar 2021
4
How To