Cisco IE-4000 Software Configuration Manual page 366

Configuring Optional Spanning-Tree Features
How to Configure the Optional Spanning-Tree Features
Default Optional Spanning-Tree Settings
Table 45 Default Optional Spanning-Tree Settings
Feature
PortFast, BPDU filtering, BPDU guard
UplinkFast
BackboneFast
EtherChannel guard
Root guard
Loop guard
How to Configure the Optional Spanning-Tree Features
Enabling Optional SPT Features
Before You Begin

Make sure that there are no loops in the network between the trunk port and the workstation or server before you
enable PortFast on a trunk port.

Use PortFast 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.

An interface with the PortFast feature enabled is moved directly to the spanning-tree forwarding state without
waiting for the standard forward-time delay.

You cannot enable both loop guard and root guard at the same time.

When you enable UplinkFast, it affects all VLANs on the switch. You cannot configure UplinkFast on an individual
VLAN.

If you enable the voice VLAN feature, the PortFast feature is automatically enabled. When you disable voice VLAN,
the PortFast feature is not automatically disabled.
Command
1. show spanning-tree active
or
show spanning-tree mst
2. configure terminal
3. spanning-tree loopguard default
4. spanning-tree portfast bpduguard default
Default Setting
Globally disabled (unless they are individually configured per
interface).
Globally disabled.
Globally disabled.
Globally enabled.
Disabled on all interfaces.
Disabled on all interfaces.
Purpose
Verifies which interfaces are alternate or root ports.
Enters global configuration mode.
Enables loop guard.
By default, loop guard is disabled.
Enables BPDU guard.
By default, BPDU guard is disabled.
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