Junos® OS For Dummies®, 2nd Edition

Understanding Network Routing

The basic routing concept is that of a route. Routes on a network, whether the global Internet or the network within your company, are the path that messages take to reach their destination.

The way routes are determined is similar to how you might choose to drive from your home to work. Most people know several different ways to get to work and each day choose the one that will be best because it's less congested, or avoids a construction project, or whatever. Network routes work the same way. The router's job is to keep track of available routes and to send network traffic along the route that it decides is best at that moment.

Most of the time, however, we tend to take the same route to work. This route is unchanging, or static. On a network, as the administrator, you may want packets from a specific router to always follow the same path to reach another router. You, again as the administrator, explicitly configure these static routes on the router.

Static routes are the simplest way to direct traffic along a path in the network and to always know what that path will be. A static route provides straightforward directions to the router. When the router sees a packet destined for a particular address in the network, the static route instructs the router to send the message to a specific IP address or out a specific interface. The IP address that the message goes to isn't necessarily the destination network, but it's generally just the next router ...