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Cisco ONS 15530 Configuration Guide and Command Reference
78-14227-01, Cisco IOS Release 12.1(10)E2
AppendixA Command Reference
Interface Configuration Commands
loopback
To configure a signal loopback on an interface, use the loopback command. To disable interface
loopback, use the no form of this command.
loopback
no loopback
Syntax Description This command has no other arguments or keywords.
Defaults Disabled
Command Modes Interface configuration
Command History
Usage Guidelines Use this command to configure line loopbacks on transparent and wave interfaces, and internal
loopbacks on waveethernetphy, or tengigethernetphy interfaces. On a transponder line card, you can
configure a loopback on either the wave interface or the transparent interface, but not both
simultaneously.
A configured loopback differs from an external loopback where you simply run a cable from the output
of a given interface to its input. Using the loopback command, you can set loopbacks without the need
to change the cabling. This is useful for remote testing, configuration, and troubleshooting.
Caution Loopbacks on waveethernetphy and tengigethernetphy interfaces disrupt service. Use this featur e with
care.
Note If you enable loopback on an interface and save the configuration to NVRAM, the interface comes
up with loopback enabled when the system boots.
Examples The following example shows how to enable loopback on a transparent i nterfac e.
Switch# configure terminal
Switch(config)# interface transparent 2/0/0
Switch(config-if)# loopback
Release Modification
12.1(10)EV2 This command was introduced.