Skip to main content

Dell PowerEdge FN I/O Module Configuration Guide 9.10(0.0)

PDF

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 1. Default Values for Port Cost
Port Cost	Default Value
1000-Mb/s Ethernet interfaces	20000
10-Gigabit Ethernet interfaces	2000
40-Gigabit Ethernet interfaces	1400
Port Channel with one 10-Gigabit Ethernet interface	2000
Port Channel with one 40-Gigabit Ethernet interface	1400
Port Channel with two 10-Gigabit Ethernet interfaces	1800
Port Channel with two 40-Gigabit Ethernet interfaces	600

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. Refer to the table for the default values.
Change the port priority of an interface. INTERFACE mode spanning-tree pvst vlan priority. The range is from 0 to 240, in increments of 16. The default is 128.

The values for interface PVST+ parameters are given in the output of the show spanning-tree pvst command, as previously shown.