L Commands for Cisco DSLAMs with NI-2

loopback

To enable a loopback on a port, use the loopback interface configuration command. To disable the loop, use the no form of the command.

loopback {diagnostic | line | payload}

no loopback {diagnostic | line | payload}

diagnostic	Transmit data is looped to receive data at the physical (PHY) layer. This option is available on all ports.
line	The external receive signal is looped to transmit at the PHY device. This option is available only on trunk and subtending ports (both OC-3 and DS3).
payload	The received payload stream is looped through the transmit stream. This option is available only on DS3 trunk and subtending ports.

Disabled

Interface configuration

Release	Modification
12.0(5)DA	This command was introduced in a previous release.

Enabling or disabling loopbacks does not untrain or retrain a port. However, removing a loopback does cause the port to retrain.

This command enables ATM local loopback for port 1 of slot 20, then disables the loopback:

DSLAM# configure terminal

DSLAM(config)# interface atm 20/1

DSLAM(config-if)# loopback diagnostic

DSLAM(config-if)# no loopback diagnostic

This command enables a line loopback for the trunk port:

DSLAM# configure terminal

DSLAM(config)# interface atm 0/1

DSLAM(config-if)# loopback line