The loopback address is the IP address of the Services Router. The loopback address ensures that the Services Router provides an IP address to management applications. Because it must always be available to hosts attempting to route packets to the Services Router, the loopback address resides on an interface that is always active, known as the loopback interface (lo0.0). Setting a loopback address ensures that the Services Router can receive packets addressed to the loopback address as long as the router is reachable though any entry (ingress) interface. In addition, applications such as NTP, RADIUS, and TACACS+ can use the loopback address as the source address for outgoing packets.
If you use the J-Web Set Up Quick Configuration page, you can either set a loopback address of your choice or have the loopback address automatically set to 127.0.0.1 when you click Apply or OK to commit the configuration.