After you install the hardware, you are ready to configure the Junos OS beyond the factory-default settings (which are not really adequate for real-world situations). To do this, you have to connect to the Junos OS running on the device.

Generally, here are the three ways to connect to the Junos OS:

  • Via the console: All Junos OS devices have an RJ-45 console port labeled CONSOLE. You can connect from a laptop or other computer using a direct crossover serial connector or through a console server. The console port does not require previous configuration, and there are no restrictions on what can be configured. Only a terminal emulation program is needed on a laptop or computer.

  • Via the CLI interface: The RJ-45 console port is not the same as the CLI port used for remote TCP/IP access (often labeled ETHERNET). Physically, they look the same, but you must configure the IP address and mask for the CLI port before using it, usually through the serial console interface.

    Once established, the dedicated management port (usually simply called fxp0) can be connected to a complete management LAN for management purposes, or through a router for global access.

  • Via the J-web interface: J-web is not a separate port, but an interface that lets you manage the Junos OS based on a graphical interface inside a web browser. Although J-web is limited when it comes to debugging operations like traceoptions, J-web is a nice way to assess overall health of a system quickly (people interpret graphics much more quickly than they can read and understand words).

Each of the three methods listed above can be used to do almost any configuration task. However, most people use the console connection initially and then switch to either the CLI or J-web for more detailed configurations, as we’ll see.

Although powerful, the console connection configuration method requires a person to be physically close to the device. The device could be located on a mountaintop, in the middle of a remote desert, or locked in a closet in the cell block of a maximum-security prison.