Use the loopback interface, lo0, as the source address for all locally generated IP packets. The lo0 interface is the interface to the router's Routing Engine.
The outgoing interface is used as the source address.
See Configure the Source Address for Locally Generated TCP/IP Packets and the JUNOS Internet Software Configuration Guide: Interfaces and Chassis.
system—To view this statement in the configuration.
system-control—To add this statement to the configuration.