Cisco Catalyst 3750-X User Manual

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Catalyst 3750-X and 3560-X Switch Software Configuration Guide
OL-21521-01
Chapter 22 Configuring Optional Spanning-Tree Features
Configuring Optional Spanning-Tree Features
You can enable this feature if your switch is running PVST+, rapid PVST+, or MSTP.
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 ports that are Port Fast-enabled (the ports are in a Port
Fast-operational state), spanning tree continues to run on the ports. They remain up unless they receive
a BPDU.
In a valid configuration, Port Fast-enabled ports do
not receive BPDUs. Receiving a BPDU on a Port
Fast-enabled port means an invalid configuration, such as the connection of an unauthorized device, and
the BPDU guard feature puts the port in the error-disabled state. When this happens, the switch shuts
down the entire port on which the violation occurred.
To prevent the port from shutting down, you can use the errdisable detect
cause bpduguard shutdown
vlan global configuration command to shut down just the offending VLAN on the port where the
violation occurred.
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.

Cisco Catalyst 3750-X Specifications

General

Switching Capacity	160 Gbps
Stacking Bandwidth	64 Gbps
Max Stacking Units	9
Layer Support	Layer 2 and Layer 3
Form Factor	Rack-mountable
DRAM	256 MB
Flash Memory	64 MB
Model	Cisco Catalyst 3750-X Series
Ports	24 or 48 10/100/1000 Ethernet ports
Uplink Interfaces	4 SFP or 2 SFP+
Features	StackWise Plus, EnergyWise
Image	IP Base or IP Services
Operating Temperature	0 to 40°C
Operating Humidity	10 to 85% noncondensing