Whenever you browse on Internet using your PC or mobile device you use a hidden whole of devices (not necessarily of your own) and protocols that allow the inter-connection to be established.

Many years ago, the most common device used to connect to a network (Internet, for example) was a dial-up modem. Nowadays, dial-up connections are decreasing significantly and are being replaced mostly by ADSL. I am not interested in to describe the whole network evolution. I prefer to speak about the protocols and devices focused in the CCNA certification.

In this chapter, I’ll be focused on the most important concepts about Computer Networking.


“History of the Internet” video.

Every networked enterprise is that which allows employees to communicate with each other using what we call an enterprise network. However, a network is not available just for medium size or big companies. Since a long time, common people at their houses enjoyed a small office/home office, or SOHO. When we sum SOHO’s plus company networks and mix them into public communication we get the widely known Internet (short form of interconnected networks).

Two or more wired or wireless interconnected devices make a network. To describe and manage the underlaying technology used to communicate these devices is the main focus of the CCNA. A networking model or networking architecture is an organized set of documents which individually describes one small function required to make a network.

There are 2 widely used networking models used by CISCO devices: The TCP/IP (Transmission Control Protocol) and the OSI (Open System Interconnection) reference model.

In the next chapter of this CISCO CCNA Crash Course you’ll be introduced to the TCP/IP model. You’ll study protocols involved on it. The same is going to be done for the OSI model.

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