Study Guide

We covered the OSI Model in CCNA Lesson 5, now we move on to the TCP/IP Model which you will also need to know for the CCNA exam.   Since internetworking is based on the TCP/IP protocol suite, the TCP/IP model is a bit more important than the OSI model on the CCNA exam.

While the ISO folks were meeting in committees to develop the OSI Reference Model, the rest of the world got busy making networks actually work and the TCP/IP suite of protocols is the result.  The TCP/IP model of networking describes how the TCP/IP protocol suite functions and operates. Simpler than the OSI Reference Model, the TCP/IP model describes the most common stack of network protocols in use today.  This network model goes by several names:   the DARPA Model, the Department of Defense (DoD) Model,  and today we just call it the TCP/IP Model.


  • Four Layers
  • De-facto standard networking
  • Models the TCP/IP protocol suite

There is a full tutorial on the TCP/IP Model here at

There are two basic network models, the OSI Model and the TCP/IP Model.  Both outline the basic functions of how networks work and are each a standard in their own right. Understanding the OSI Reference Model is a requirement for passing any exam on networking whether it is the CCNA, CCNP, Network+ or any Juniper exam.

Memorize the OSI Reference Model. Now. You’ll use it over and over again and none of the information we cover from here on will make any sense if you don’t.  Networks were built one layer at a time over a period of time.  First physical communication was made possible, then logical addresses were used to  allow you to move computers around on a network. Next, the ability to route packets from one network to another was worked out, then ways to guarantee delivery of large volumes of data and finally ways to boot up and to manage the network, provide names humans can remember, and finally to serve up stored data as web pages.

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Networks can be described in terms of their physical layout, called a topology. A network's topology will often determine the characteristics of the network, whether it broadcasts data or communicates point-to-point, whether it will have unidirectional or bidirectional communication, how many end stations can be attached to it and many other factors. The logical topology will determine which end stations attached to it operate in discrete units and how data will be exchanged. Continue reading

Welcome to the next lesson in the CCNA Lessons Tutorial and Study Guide series.

The CCNA exam tests your knowledge of network types, uses, topologies and architectures, the network equipment used to build them, and the knowledge of how to build, configure and maintain internetworks.  You should be able to explain what each type of equipment will do and how it will improve the network.  You will need to know the benefits and drawbacks of each network type, the kinds of communications used in networks, the problems networks experience as they grow, how networks may be extended. Most importantly, you must understand how and when to segment networks into switched and routed domains to improve network performance using switching, VLANs and routing.   The process of understanding networking begins with understanding what networks are, how they are structured and how they work.

This tutorial begins the process by defining what a network is and explaining the common structures used by most networks, called “topologies”.  You will need to know the strengths and weaknesses of each of these network topologies to succeed with the CCNA exam.

Let’s move on to the definition of a network.

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