Every skill set comes with a history of time and effort spent
learning those foundational concepts that allow you to become
proficient in a specific area. You are about to embark on a
journey through one of those critical areas where understanding and true investment in the
material can improve your technical understanding, your career, and your odds of passing
the CEH exam. This is where it all begins—understanding those key fundamental concepts
that give you a basis on which all other more complex subjects can firmly rest.
In this chapter we’ll delve into some basic concepts, most of which system administrators
and network administrators should be comfortable with. These fundamentals are critical
to building a solid base for the more advanced topics yet to come. We’ll take a step-by-step
walk-through on key concepts such as the OSI model, the TCP/IP suite, subnetting, network
appliances and devices, cloud technologies, and good old-fashioned client system concepts
and architectures. Ever hear the phrase “where the rubber hits the road”? Well, consider this
a burnout across a quarter-mile drag strip. Let’s dig in and devour this material!
Exploring Network Topologies
Whether you are a veteran or a novice—or just have a bad memory—a review of network-
ing technologies is helpful and an important part of understanding the attacks and defenses
we’ll explore later on.
Network topologies represent the physical side of the network, and they form part of
the foundation of our overall system. Before we explore too far, the first thing you need to
understand is that you must consider two opposing yet related concepts in this section: the
physical layout of the network and the logical layout of the network. The physical layout
of a network relates directly to the wiring and cabling that connects devices. Some of the
common layouts we’ll cover are the bus, ring, star, mesh, and hybrid topologies. The logical
layout of the network equates to the methodology of access to the network, the stuff you
can’t readily see or touch, or the flow of information and other data. We’ll get to the logical
side, but first let’s break down each physical design:
Bus The bus topology (Figure 2.1) lays out all connecting nodes in a single run that acts
as the common backbone connection for all connected devices. As with the public trans-
port of the same name, signals get on, travel to their destination, and get off. The bus is the
common link to all devices and cables. The downside to its simplicity is its vulnerability; all
connectivity is lost if the bus backbone is damaged. The best way to envision this vulner-
ability is to think of those strings of Christmas lights that go completely out when one light