Cisco 3750G - Catalyst Integrated Wireless LAN Controller, Руководство по настройке

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20-13
Catalyst 3750 Switch Software Configuration Guide
OL-8550-02
Chapter 20 Configuring Optional Spanning-Tree Features
Configuring Optional Spanning-Tree Features
Beginning in privileged EXEC mode, follow these steps to enable Port Fast. This procedure is optional.
Note You can use the spanning-tree portfast default global configuration command to globally enable the
Port Fast feature on all nontrunking ports.
To disable the Port Fast feature, use the spanning-tree portfast disable interface configuration
command.
Enabling BPDU Guard
When you globally enable BPDU guard on interfaces that are Port Fast-enabled (the interfaces are in a
Port Fast-operational state), spanning tree shuts down Port Fast-enabled interfaces that receive BPDUs.
In a valid configuration, Port Fast-enabled interfaces do not receive BPDUs. Receiving a BPDU on a
Port Fast-enabled interface signals an invalid configuration, such as the connection of an unauthorized
device, and the BPDU guard feature puts the interface in the error-disabled state. The BPDU guard
feature provides a secure response to invalid configurations because you must manually put the interface
back in service. Use the BPDU guard feature in a service-provider network to prevent an access port
from participating in the spanning tree.
Caution
Configure Port Fast only on interfaces that connect to end stations; otherwise, an accidental topology
loop could cause a data packet loop and disrupt switch and network operation.
Command Purpose
Step 1 configure terminal Enter global configuration mode.
Step 2 interface interface-id Specify an interface to configure, and enter interface
configuration mode.
Step 3 spanning-tree portfast [ trunk ] Enable Port Fast on an access port connected to a single
workstation or server. By specifying the
trunk keyword, you can
enable Port Fast on a trunk port.
Note
To enable Port Fast on trunk ports, you must use the
spanning-tree portfast trunk interface configuration
command. The spanning-tree portfast command will
not work on trunk ports.
Caution
Make sure that there are no loops in the network
between the trunk port and the workstation or server
before you enable Port Fast on a trunk port.
By default, Port Fast is disabled on all interfaces.
Step 4 end Return to privileged EXEC mode.
Step 5
show spanning-tree interface interface-id
portfast
Verify your entries.
Step 6
copy running-config startup-config (Optional) Save your entries in the configuration file.