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

Configuring Optional Spanning-Tree Features
•
•
•
•

Default Optional Spanning-Tree Configuration

Table 15-1
Table 15-1
Feature
Port Fast, BPDU
filtering, BPDU guard
UplinkFast
CSUF
BackboneFast
EtherChannel guard
Root guard
Loop guard

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, the BackboneFast, or the cross-stack UplinkFast 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

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+, rapid PVST+, or MSTP.
Catalyst 2950 and Catalyst 2955 Switch Software Configuration Guide
15-14
Enabling BackboneFast, page 15-19
Enabling EtherChannel Guard, page 15-20
Enabling Root Guard, page 15-21
Enabling Loop Guard, page 15-21
shows the default optional spanning-tree configuration.
Default Optional Spanning-Tree Configuration
Default Setting
Globally disabled (unless they
are individually configured
per interface).
Globally disabled.
Disabled on all interfaces.
Globally disabled.
Globally enabled.
Disabled on all interfaces.
Disabled on all interfaces.
Chapter 15
(optional)
(optional)
(optional)
(optional)
Configuring Optional Spanning-Tree Features
Chapter 18,
78-11380-12