About Etherchannel Guard - Cisco Catalyst 4500 Series Configuration Manual

About EtherChannel Guard

About EtherChannel Guard
EtherChannel guard allows you to detect an EtherChannel misconfiguration between the switch and a
connected device. A misconfiguration can occur if the interfaces of a switch are manually configured in
an EtherChannel, and one or more interfaces on the other device are not. For EtherChannel configuration
guidelines, see the
Note EtherChannel guard applies only to EtherChannels in forced mode (that is, manually configured) rather
than through PAgP or LACP.
If the switch detects a misconfiguration on the other device, EtherChannel guard error-disables all
interfaces in the EtherChannel bundle, and displays an error message.
You can enable this feature with the spanning-tree etherchannel guard misconfig global configuration
command.
Enabling EtherChannel Guard (Optional)
You can enable EtherChannel guard to detect an EtherChannel misconfiguration if your switch is
running PVST+, rapid PVST+, or MSTP.
To enable EtherChannel guard, perform this task:
Command
Step 1
Switch(config)# configure terminal
Step 2
Switch(config)# spanning-tree etherchannel guard
misconfig
Step 3
Switch(config)# end
Step 4
Switch(config)# show spanning-tree summary
Step 5
Switch(config)# copy running-config
startup-config
To disable the EtherChannel guard feature, use the no spanning-tree etherchannel guard misconfig
global configuration command.
Use the show interfaces status err-disabled privileged EXEC command to show which switch ports are
disabled because of an EtherChannel misconfiguration. On the remote device, you can enter the show
etherchannel summary privileged EXEC command to verify the EtherChannel configuration.
After the configuration is corrected, enter the shutdown and no shutdown interface configuration
commands on the port-channel interfaces that were misconfigured.
About PortFast
Spanning Tree PortFast causes an interface configured as a Layer 2 access port to enter the forwarding
state immediately, bypassing the listening and learning states. Use PortFast on Layer 2 access ports
connected to a single workstation or server to allow those devices to connect to the network immediately,
rather than waiting for spanning tree to converge. Even if the interface receives a bridge protocol data
Software Configuration Guide—Release IOS XE 3.3.0SG and IOS 15.1(1)SG
23-6
"EtherChannel Configuration Guidelines and Restrictions" section on page
Chapter 23
Purpose
Enters global configuration mode.
Enables EtherChannel guard.
Returns to privileged EXEC mode.
Verifies your entries.
(Optional) Saves your entries in the configuration file.
Configuring Optional STP Features
24-5.
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