Reference Guide

Modifying Global Parameters
You can modify the spanning tree parameters. The root bridge sets the values for forward-delay, hello-time, and max-age and
overwrites the values set on other bridges participating in STP.
NOTE: Dell Networking recommends that only experienced network administrators change the spanning tree parameters.
Poorly planned modification of the spanning tree parameters can negatively affect network performance.
The following table displays the default values for STP.
Table 68. STP Default Values
STP Parameters Default Value
Forward Delay 15 seconds
Hello Time 2 seconds
Max Age 20 seconds
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
● 19
● 4
● 2
● 18
● 3
● 1
Port Priority 8
● Change the forward-delay parameter (the wait time before the interface enters the Forwarding state).
PROTOCOL SPANNING TREE mode
forward-delay seconds
The range is from 4 to 30.
The default is 15 seconds.
● Change the hello-time parameter (the BPDU transmission interval).
PROTOCOL SPANNING TREE mode
hello-time seconds
NOTE:
With large configurations (especially those 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 (the refresh interval for configuration information that is generated by recomputing the
spanning tree topology).
PROTOCOL SPANNING TREE mode
max-age seconds
The range is from 6 to 40.
The default is 20 seconds.
To view the current values for global parameters, use the show spanning-tree 0 command from EXEC privilege mode.
Refer to the second example in Enabling Spanning Tree Protocol Globally.
734
Spanning Tree Protocol (STP)