Setup Guide
• Hello-time — the time interval in which the bridge sends bridge protocol data units (BPDUs).
• Max-age — the length of time the bridge maintains conguration information before it refreshes that information by recomputing the
PVST+ topology.
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 congurations (especially those congurations with more ports), Dell EMC 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 — inuences 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.
Table 72. Default Values for Port Cost
Port Cost Default Value
100-Mb/s Ethernet interfaces 200000
1-Gigabit Ethernet interfaces 20000
10-Gigabit Ethernet interfaces 2000
25-Gigabit Ethernet interfaces 1700
Per-VLAN Spanning Tree Plus (PVST+) 663