Modifying Interface Pvst+ Parameters - Dell S4048–ON Configuration Manual

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.
Table 68. Default Values for Port Cost
Port Cost
100-Mb/s Ethernet interfaces
1-Gigabit Ethernet interfaces
10-Gigabit Ethernet interfaces
Port Channel with 100 Mb/s Ethernet interfaces
Port Channel with 1-Gigabit Ethernet interfaces
Port Channel with 10-Gigabit Ethernet interfaces
NOTE: The Dell Networking OS implementation of PVST+ uses IEEE 802.1s costs as the default costs. Other
implementations use IEEE 802.1w costs as the default costs. If you are using Dell Networking systems in a multi-vendor
network, verify that the costs are values you intended.
To change the port cost or port priority of an interface, use the following commands.
• Change the port cost of an interface.
INTERFACE mode
spanning-tree pvst vlan cost.
The range is from 0 to 200000.
672
Per-VLAN Spanning Tree Plus (PVST+)
Default Value
200000
20000
2000
180000
18000
1800