Optional Spanning-Tree Configuration Guidelines; Enabling Port Fast - Cisco 3020 - Catalyst Blade Switch Configuration Manual

Configuring Optional Spanning-Tree Features

Optional Spanning-Tree Configuration Guidelines

You can configure PortFast, BPDU guard, BPDU filtering, EtherChannel guard, root guard, or loop
guard if your switch is running PVST+, rapid PVST+, or MSTP.
You can configure the UplinkFast or the BackboneFast feature for rapid PVST+ or for the MSTP, but the
feature remains disabled (inactive) until you change the spanning-tree mode to PVST+.

Enabling Port Fast

An interface with the Port Fast feature enabled is moved directly to the spanning-tree forwarding state
without waiting for the standard forward-time delay.
Use Port Fast only when connecting a single end station to an access or trunk port. Enabling this feature
Caution
on an interface connected to a switch or hub could prevent spanning tree from detecting and disabling
loops in your network, which could cause broadcast storms and address-learning problems.
If you enable the voice VLAN feature, the Port Fast feature is automatically enabled. When you disable
voice VLAN, the Port Fast feature is not automatically disabled. For more information, see
"Configuring Voice VLAN."
You can enable this feature if your switch is running PVST+, rapid PVST+, or MSTP.
Beginning in privileged EXEC mode, follow these steps to enable Port Fast. This procedure is optional.
Command
Step 1 configure terminal
Step 2
interface interface-id
Step 3
spanning-tree portfast [trunk]
Step 4 end
Step 5 show spanning-tree interface interface-id
portfast
Step 6
copy running-config startup-config
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Chapter 15
Purpose
Enter global configuration mode.
Specify an interface to configure, and enter interface
configuration mode.
Enable Port Fast on an access port connected to a single
workstation or server. By specifying the trunk keyword, you can
enable Port Fast on a trunk port.
To enable Port Fast on trunk ports, you must use the
Note
spanning-tree portfast trunk interface configuration
command. The spanning-tree portfast command will
not work on trunk ports.
Make sure that there are no loops in the network
Caution
between the trunk port and the workstation or server
before you enable Port Fast on a trunk port.
By default, Port Fast is disabled on all interfaces.
Return to privileged EXEC mode.
Verify your entries.
(Optional) Save your entries in the configuration file.
Configuring Optional Spanning-Tree Features
Chapter 12,
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