Cisco CATALYST 2960

18-12
Catalyst 2960 and 2960-S Switches Software Configuration Guide, Release 15.0(1)SE
OL-26520-01
Chapter 18 Configuring Optional Spanning-Tree Features
Configuring Optional Spanning-Tree Features
• Enabling BPDU Guard, page 18-13 (optional)
• Enabling BPDU Filtering, page 18-14 (optional)
• Enabling UplinkFast for Use with Redundant Links, page 18-15 (optional)
• Enabling Cross-Stack UplinkFast, page 18-16 (optional)
• Enabling BackboneFast, page 18-17 (optional)
• Enabling EtherChannel Guard, page 18-17 (optional)
• Enabling Root Guard, page 18-18 (optional)
• Enabling Loop Guard, page 18-18 (optional)
Default Optional Spanning-Tree Configuration
Table 18-1 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.
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
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.
Table 18-1 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 2960-S switches, the
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.