Chapter Summary
The key points covered in this chapter are as follows.
- Routing is one of the complicated functions of IP. Routers receive packets and forward them on toward their destinations.
- Complex internetworks can have redundant routers that provide multiple paths to the same destination. The job of a router is to forward packets using the most efficient path.
- A router can be a standalone hardware device, an operating system, or a separate software product.
- Routers store information about the network in a routing table. When forwarding a packet, the router searches the table for a route to each destination and transmits the packet to the appropriate destination.
- When a router fails to locate a route to a particular destination in the table, it sends the packet to the designated default gateway.
- Information gets into the routing table in two ways: using either static routing, which is the manual creation and maintenance of table entries, or dynamic routing, which uses specialized routing protocols to update the table.
- The Windows 2000 Route.exe and other such programs provide direct access to the routing table, usually from the command line. Administrators can use these tools to display, add, delete, and change routing table entries.
- Dynamic routing enables routers to share the information in their tables with the other routers on the network.
- RIP is the most common routing protocol used today; it relies predominantly on broadcast transmissions to share routing table information and uses the number of hops to the destination as its metric.
- OSPF is a more advanced routing protocol that uses link-state routing, which measures the actual efficiency of a route rather than simply counting the number of hops.