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Catalyst 3550 Multilayer Switch Software Configuration Guide
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Chapter 10 Configuring STP
Configuring Advanced STP Features
Configuring Advanced STP Features
These sections include advanced STP configuration information:
• Configuring Port Fast, page 10-32
• Configuring BPDU Guard, page 10-33
• Configuring UplinkFast for Use with Redundant Links, page 10-34
• Configuring Cross-Stack UplinkFast, page 10-35
• Configuring BackboneFast, page 10-36
• Configuring Root Guard, page 10-36
• Enabling EtherChannel Guard, page 10-37
Configuring Port Fast
A port with the Port Fast feature enabled is moved directly to the spanning-tree forwarding state without
waiting for the standard forward-time delay.
Caution Use Port Fast only when connecting a single end station to a Layer 2 access port. Enabling this feature
on an interface connected to a switch or hub could prevent STP from detecting and disabling loops
in your network, which could cause broadcast storms and address-learning problems.
Beginning in privileged EXEC mode, follow these steps to enable Port Fast on a Layer 2 access port:
To disable the Port Fast feature, use the no spanning-tree portfast interface configuration command.
Command Purpose
Step 1
configure terminal Enter global configuration mode.
Step 2
interface interface-id Enter interface configuration mode, and specify an interface to
configure. Valid interfaces include physical interfaces and
port-channel logical interfaces (port-channel
port-channel-number).
Step 3
spanning-tree portfast Enable Port Fast on a Layer 2 access port connected to a single
workstation or server.
By default, Port Fast is disabled on all interfaces.
Step 4
end Return to privileged EXEC mode.
Step 5
show running interface interface-id Verify your entries.
Step 6
copy running-config startup-config (Optional) Save your entries in the configuration file.