Cisco ASR 9000 Series Command Reference Guide

loopback (T3/E3)
To loop the entire T3 or E3 line (all 28 T1 channels or all 21 E1 channels) on the T3 controller or E3 controller,
use the loopback command in T3 or E3 configuration mode. To remove the loop, use the no form of this
command.
loopback {local| {network| remote {line| payload}}}
no loopback
Syntax Description
Loops the data back toward the router and sends an alarm indication signal (AIS)
out toward the network.
local
Sets the loopback toward the network before going through the framer (line) or
after going through the framer (payload).
network {line | payload}
Sends a far-end alarm control (FEAC) request to the remote end requesting that
it enter into a network line loopback. FEAC requests (and therefore remote
loopbacks) are possible only when the T3 is configured for C-bit framing. The
M23 format does not support remote loopbacks.
remote {line | payload}
Command Default
No loops are configured on the T3 line.
Command Modes
T3 configuration
E3 configuration
Command History
This command was introduced.Release 3.9.0
Support for E3 configuration was added.Release 4.0.0
Usage Guidelines
Use the loopback command for troubleshooting purposes. To verify that a loopback is configured on the
interface, use the show controllers t3 or show controllers e3 command in EXEC mode. Note that remote
loopback is valid only in C-bit parity mode.
You can also loopback each T1 or E1 channel by using the loopback command in T1 or E1 configuration
mode.
Task ID
OperationsTask ID
read, writesonet-sdh
Cisco ASR 9000 Series Aggregation Services Router Interface and Hardware Component Command Reference,
Release 5.3.x
1025
T3, E3, T1, E1 Controller Commands on the Cisco ASR 9000 Series Router
loopback (T3/E3)

Cisco ASR 9000 Series Specifications

General

Series	ASR 9000
Category	Network Router
Modular Design	Yes
Redundancy	Yes (Hardware and Software)
Operating System	Cisco IOS XR
Interfaces/Ports	10G, 40G, 100G, 400G Ethernet
Expansion Slots	Varies by model
Routing Protocol	BGP, OSPF, IS-IS, EIGRP
Management	CLI, SNMP, NETCONF
Power Supply	Redundant
Port Density	Varies by model
Power Supply Options	AC, DC
Memory	Varies by model
Storage	Varies by model
Dimensions	Varies by model
Weight	Varies by model