Juniper PHYSICAL LAYER - CONFIGURATION GUIDE V11.1.X Configuration Manual page 170

JUNOSe 11.1.x Physical Layer Configuration Guide
path ds1|e1 loopback
path ds3 loopback
148
Testing Interfaces
Example
host1(config)#controller sonet 4/0
host1(config-controller)#loopback network
Use the no version to disable loopback.
See loopback.
Use to configure a loopback at the T1/E1 over SONET/SDH VT layer.
Specify one of the following options:
local Loops the router output data back toward the router at the T1/E1
framer; on supported line modules, also sends an alarm indication signal
(AIS) out toward the network.
network { line | payload }
Specify the line keyword to loop the data back toward the network before
the T1/E1 framer and automatically set a local loopback at the HDLC
controllers.
Specify the payload keyword to loop the payload data back toward the
network at the T1/E1 framer and automatically set a local loopback at
the HDLC controllers.
Example
host1(config-controll)#path 12 ds1 1/3/4 loopback network line
Use the no version to clear the local loopback configuration.
See path ds1|e1 loopback.
Use to configure a loopback at the T3 layer.
Specify one of the following options:
local Loops the data back toward the router; on supported line modules,
also sends an alarm indication signal (AIS) out toward the network.
network { line | payload }
Specify the line keyword to loop the data toward the network before the
data reaches the framer.
Specify the payload keyword to loop the data toward the network after
the framer has processed the data.
Example
host1(config-controll)#controller sonet 5/0
host1(config-controll)#path 12 ds3 1 loopback local