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Cisco Catalyst Switch Module 3110 and 3012 for IBM BladeCenter Software Configuration Guide
OL-12189-01
Chapter 19 Configuring Optional Spanning-Tree Features
Configuring Optional Spanning-Tree Features
• Enabling Cross-Stack UplinkFast, page 19-16 (optional and only on the Catalyst Switch
Module 3110)
• Enabling BackboneFast, page 19-16 (optional)
• Enabling EtherChannel Guard, page 19-17 (optional)
• Enabling Root Guard, page 19-18 (optional)
• Enabling Loop Guard, page 19-18 (optional)
Default Optional Spanning-Tree Configuration
Table 19-1 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 Switch Module 3110, 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 Switch Module 3012, 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.
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 19-1 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 the Catalyst Switch Module 3110, 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.
