Default Optional Spanning-Tree Configuration; Enabling Port Fast - Cisco Catalyst 2950 Software Configuration Manual

Configuring Optional Spanning-Tree Features

Default Optional Spanning-Tree Configuration

Table 12-1
Table 12-1 Default Optional Spanning-Tree Configuration
Feature
Port Fast, BPDU filtering, BPDU guard
UplinkFast
CSUF
BackboneFast
Root guard
Loop guard

Enabling 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.
Use Port Fast only when connecting a single end station to an access or trunk port. Enabling this feature
Caution
on a port 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 or MSTP. The MSTP is available only if you
have the enhanced software image installed on your switch.
Beginning in privileged EXEC mode, follow these steps to enable Port Fast:
Command
Step 1 configure terminal
Step 2
interface interface-id
Step 3 spanning-tree portfast [trunk]
Catalyst 2950 Desktop Switch Software Configuration Guide
12-14
shows the default optional spanning-tree configuration.
Chapter 12
Default Setting
Globally disabled on the switch (unless they are individually
configured per interface).
Disabled on the switch.
Disabled on all interfaces.
Disabled on the switch.
Disabled on all interfaces.
Disabled on all interfaces.
Purpose
Enter global configuration mode.
Enter interface configuration mode, and specify an interface to
configure.
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.
Caution Make sure that there are no loops in the network
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 ports.
Configuring Optional Spanning-Tree Features
Chapter 15,
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