Enabling Port Fast - Cisco Catalyst 3750-E Software Configuration Manual

Configuring Optional Spanning-Tree Features
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Default Optional Spanning-Tree Configuration
Table 20-1
Table 20-1 Default Optional Spanning-Tree Configuration
Feature
Port Fast, BPDU filtering, BPDU guard
UplinkFast
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.
On a Catalyst 3750-E switch, 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+.
On a Catalyst 3560-E switch, 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."
Catalyst 3750-E and 3560-E Switch Software Configuration Guide
20-12
Enabling BackboneFast, page 20-16
Enabling EtherChannel Guard, page 20-17
Enabling Root Guard, page 20-18
Enabling Loop Guard, page 20-18
shows the default optional spanning-tree configuration.
Chapter 20
(optional)
(optional)
(optional)
(optional)
Default Setting
Globally disabled (unless they are individually configured
per interface).
Globally disabled. (On Catalyst 3750-E switches, the
UplinkFast feature is the CSUF feature.)
Globally disabled.
Globally enabled.
Disabled on all interfaces.
Disabled on all interfaces.
Configuring Optional Spanning-Tree Features
Chapter 15,
OL-9775-08