Routing is the process of sending data from a host on one network or VLAN to a remote host on another network or VLAN through a router or routers. Routed networks range from simple site to site fixed or dial up links to the Internet. Based at Layer 3, routers base decisions on logical addresses rather than the Layer 2 physical addresses used by switches.
Using the available Layer 3 information, routers can choose the best path based on cost, bandwidth, delay along with many other variables. Access control lists can be applied to limit access between separate networks. Routers can use three options for route selection;
- Static Routing - Set by the system administrator, static routes ensure traffic will always follow a pre determined route through the network. Static routes are ideal for small networks however become impracticable on larger networks when hundreds if not thousands or route are required.
- Dynamic Routing - Designed to select the best route based on various configurable options, dynamic routing provides scalability with the minimum of configuration.
- Default Routing - Used to direct all traffic of unknown destination.
