Reference Guide

690 | Spanning Tree Protocol
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To change STP global parameters:
View the current values for global parameters using the
show spanning-tree 0 command from EXEC
privilege mode. See Figure 38-5.
Modifying Interface STP Parameters
You can set the port cost and port priority values of interfaces in Layer 2 mode.
• Port cost is a value that is based on the interface type. The greater the port cost, the less likely the port
will be selected to be a forwarding port.
• Port priority influences the likelihood that a port will be selected to be a forwarding port in case that
several ports have the same port cost.
The default values are listed in Table 38-2.
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 Networking 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
Table 38-2. STP Default Values
STP Parameter Default Value