Loopback (Ethernet) - Cisco ASR 9000 Series Command Reference Manual

Ethernet Interface Commands on the Cisco ASR 9000 Series Router

loopback (Ethernet)

To configure an Ethernet controller for loopback mode, use the loopback command in interface configuration
mode. To disable loopback, use the no form of this command.
loopback {external| internal| line}
no loopback
Syntax Description
external
internal
line
Command Default
Loopback mode is disabled.
Command Modes
Interface configuration
Command History
Release
Release 3.7.2
Usage Guidelines
To use this command, you must be in a user group associated with a task group that includes appropriate task
IDs. If the user group assignment is preventing you from using a command, contact your AAA administrator
for assistance.
The loopback command is available for all Ethernet interface types (Gigabit Ethernet, 10-Gigabit Ethernet).
Two loopback operation modes are supported for diagnostic purposes: internal and line. In the terminal
(internal) loopback, the sent signal is looped back to the receiver. In the facility (line) loopback, the signal
received from the far end is looped back and sent on the line. The two loopback modes cannot be active at
the same time. In normal operation mode, neither of the two loopback modes is enabled.
Use the loopback external command when an external loopback connector is attached to the interface.
Tip
All IPv4 self-ping packets are sent out of the interface and looped back externally
before being received on the ingress path.
All packets are looped back internally within the router before reaching an external
cable.
Incoming network packets are looped back through the external cable.
Cisco ASR 9000 Series Aggregation Services Router Interface and Hardware Component Command Reference,
Modification
This command was first introduced.

loopback (Ethernet)

Release 5.3.x
97