Cisco Systems 3750E Manual De Usuario
20-12
Catalyst 3750-E and 3560-E Switch Software Configuration Guide
OL-9775-02
Chapter 20 Configuring Optional Spanning-Tree Features
Configuring Optional Spanning-Tree Features
•
(optional)
•
(optional)
•
(optional)
•
(optional)
Default Optional Spanning-Tree Configuration
shows the default optional spanning-tree configuration.
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.
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+.
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+.
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.
without waiting for the standard forward-time delay.
Caution
Use Port Fast only when connecting a single end station to an access or trunk port. Enabling this feature
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.
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
voice VLAN, the Port Fast feature is not automatically disabled. For more information, see
Table 20-1
Default Optional Spanning-Tree Configuration
Feature
Default Setting
Port Fast, BPDU filtering, BPDU guard
Globally disabled (unless they are individually configured
per interface).
per interface).
UplinkFast
Globally disabled. (On Catalyst 3750-E switches, the
UplinkFast feature is the CSUF feature.)
UplinkFast feature is the CSUF feature.)
BackboneFast
Globally disabled.
EtherChannel guard
Globally enabled.
Root guard
Disabled on all interfaces.
Loop guard
Disabled on all interfaces.