Specifications

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Cisco MWR 2941 Mobile Wireless Edge Router Release 3.5 Software Configuration Guide, Cisco IOS Release 15.1(3)MR
OL-26895-01
Chapter 11 Configuring Optional Spanning-Tree Features
Configuring Optional Spanning-Tree Features
Configuring Optional Spanning-Tree Features
• Default Optional Spanning-Tree Configuration, page 11-5
• Optional Spanning-Tree Configuration Guidelines, page 11-5
• Enabling Port Fast, page 11-5 (optional)
• Enabling BPDU Guard, page 11-6 (optional)
• Enabling BPDU Filtering, page 11-7 (optional)
• Enabling Root Guard, page 11-8 (optional)
• Enabling Loop Guard, page 11-9 (optional)
Default Optional Spanning-Tree Configuration
Table 11-1 shows the default optional spanning-tree configuration. Only NNIs or ENIs with STP enabled
participate in STP on the router. UNIs and ENIs that have not been configured for STP are always in the
forwarding state.
Optional Spanning-Tree Configuration Guidelines
You can configure PortFast, BPDU guard, BPDU filtering, root guard, or loop guard if your router is
running PVST+ or MSTP.
Enabling Port Fast
An STP port 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.
You can enable this feature if your router is running PVST+ or MSTP.
Table 11-1 Default Optional Spanning-Tree Configuration
Feature Default Setting
Port Fast, BPDU filtering, BPDU guard Globally disabled (unless they are individually configured per STP port).
Root guard Disabled on all STP ports.
Loop guard Disabled on all STP ports.