Cisco Catalyst 3750-E User Manual

20-12
Catalyst 3750-E and 3560-E Switch Software Configuration Guide
OL-9775-08
Chapter 20 Configuring Optional Spanning-Tree Features
Configuring Optional Spanning-Tree Features
• Enabling BackboneFast, page 20-16 (optional)
• Enabling EtherChannel Guard, page 20-17 (optional)
• Enabling Root Guard, page 20-18 (optional)
• Enabling Loop Guard, page 20-18 (optional)
Default Optional Spanning-Tree Configuration
Table 20-1 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.
On a Catalyst 3750-E switch, you can configure the UplinkFast, the BackboneFast, or the cross-stack
Up
linkFast 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
PV
ST+ 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.
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.
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 Chapter 15,
“Configuring Voice VLAN.”
Ta b l e 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).
UplinkFast Globally disabled. (On Catalyst 3750-E switches, the
U
plinkFast feature is the CSUF feature.)
BackboneFast Globally disabled.
EtherChannel guard Globally enabled.
Root guard Disabled on all interfaces.
Loop guard Disabled on all interfaces.

Cisco Catalyst 3750-E Specifications

General

Series	Catalyst 3750-E
Switching Capacity	32 Gbps
Stacking Bandwidth	32 Gbps
StackWise Plus	Yes
Layer Support	Layer 3
MAC Address Table Size	12, 000 entries
RAM	256 MB
Flash Memory	64 MB
Memory	256 MB DRAM, 64 MB Flash
Operating Temperature	32 to 113°F (0 to 45°C)
Ports	48 10/100/1000 Ethernet ports
Form Factor	Rack-mountable
Jumbo Frame Support	Yes
Input Voltage	100 to 240 VAC
Storage Temperature	-25 to 70 °C
Relative Humidity	10 to 90% non-condensing