Reference Guide

Spanning Tree Protocol (STP) | 951
Modifying Global Parameters
You can modify 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 Spanning Tree.
Table 48-2 displays the default values for Spanning Tree.
To change STP global parameters:
Note: Dell Force10 recommends that only experienced network administrators change the Spanning Tree
parameters. Poorly planned modification of the Spanning Tree parameters can negatively impact network
performance.
Table 48-2. STP Default Values
STP Parameter Default Value
Forward Delay 15 seconds
Hello Time 2 seconds
Max Age 20 seconds
Port Cost 100-Mb/s Ethernet interfaces 19
1-Gigabit Ethernet interfaces 4
10-Gigabit Ethernet interfaces 2
Port Channel with 100 Mb/s Ethernet interfaces 18
Port Channel with 1-Gigabit Ethernet interfaces 3
Port Channel with 10-Gigabit Ethernet interfaces 1
Port Priority 8
Task Command Syntax Command Mode
Change the forward-delay parameter (the wait time before the
interface enters the forwarding state).
• Range: 4 to 30
• Default: 15 seconds
forward-delay seconds PROTOCOL
SPANNING TREE
Change the hello-time parameter (the BPDU transmission interval).
Note: With large configurations (especially those with more
ports) Dell Force10 recommends that you increase the
hello-time.
Range: 1 to 10
Default: 2 seconds
hello-time seconds PROTOCOL
SPANNING TREE
Change the max-age parameter (the refresh interval for configuration
information that is generated by recomputing the Spanning Tree
topology).
Range: 6 to 40
Default: 20 seconds
max-age seconds PROTOCOL
SPANNING TREE