The Route Table
Configuring Static Routes
Case Study: Simple Static Routes
Case Study: Summary Routes
Case Study: Alternative Routes
Case Study: Static Floating Routes
Case Study: Load Sharing
Case Study: Recursive Table Lookups
Troubleshooting Static Routes
Case Study: Tracing a Failed Route
Case Study: A Protocol Conflict
An important observation from Chapter 2, "TCP/IP Review," is that the data link/physical layers and the
transport/network layers, as defined by the OSI model, perform very similar duties: They provide the
means for conveying data from a source to a destination across some path. The difference is that the data
link/physical layers provide communications across a physical path, whereas the transport/network layers
provide communications across a logical or virtual path made up of a series of data links.
Further, Chapter 2 showed that for communications to take place across a physical path, certain
information about data link identifiers and encapsulations must be acquired and stored in a database such
as the ARP cache. Similarly, information that the transport/network layers require to do their job must
also be acquired and stored. This information is stored in the route table, also known as the forwarding
database.
This chapter examines what sort of information is required to route a packet, how that information is
stored in the route table, how to enter the information into the database, and some techniques for building
a routed internetwork by entering the proper information into the proper routers' route tables.