CCNA: OSI Reference Model

A major part of the CCNA exam focuses on your knowledge of the OSI Reference Model and its seven layer approach to network activities, functions, data formats, and communications. Of course, there is more emphasis in those layers of the model that deal with routing and routers, but every layer in the reference model is included on the exam. As you prepare for the exam, be sure this is an area you know and understand in detail.