When you first connect a management PC or laptop to a built-in Ethernet port on a Services Router, the router acts as a DHCP client and attempts to perform an autoinstallation. If it does not find a DHCP server, the router assigns 192.168.1.1/24 as the IP address for port 0. (If you are connected to port 1, 192.168.2.1/24 is assigned as the IP address. Port 2 and port 3 are assigned 192.168.3.1/24 and 192.168.4.1/24, respectively.)
Because this address is not part of any explicit configuration, it is removed when you change the configuration in any way. You must configure an IP address for this LAN port when you commit your initial configuration. (See Step 2. Configuring Basic Settings with J-Web Quick Configuration or Step 2. Configuring Basic Settings with the CLI.)