Administrator Guide

To change PVST+ parameters on the root bridge, use the following commands.
• Change the forward-delay parameter.
PROTOCOL PVST mode
vlan forward-delay
The range is from 4 to 30.
The default is 15 seconds.
• Change the hello-time parameter.
PROTOCOL PVST mode
vlan hello-time
NOTE: With large configurations (especially those configurations with more ports), Dell Networking
recommends increasing the hello-time.
The range is from 1 to 10.
The default is 2 seconds.
• Change the max-age parameter.
PROTOCOL PVST mode
vlan max-age
The range is from 6 to 40.
The default is 20 seconds.
The values for global PVST+ parameters are given in the output of the show spanning-tree pvst
command.
Modifying Interface PVST+ Parameters
You can adjust two interface parameters (port cost and port priority) to increase or decrease the probability
that a port becomes a forwarding port.
• 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 following tables lists the default values for port cost by interface.
Per-VLAN Spanning Tree Plus (PVST+) 715