Loopback Address for the SRX 210 Services Gateway
The loopback address is the IP address of the SRX 210 services gateway. The loopback address ensures that the device provides an IP address to management applications. Because it must always be available to hosts attempting to route packets to the device, 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 device can receive packets addressed to the loopback address as long as the device is reachable though any entry (ingress) interface. In addition, applications such as NTP (Network Time Protocol), RADIUS (Remote Authentication Dial-In User Service), and TACACS+ (Terminal Access Controller Access-Control System Plus) can use the loopback address as the source address for outgoing packets.
If you use the J-Web Quick Configuration Set Up 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.