Hexadecimal vs. Binary 35
You’ll want to become comfortable with TCP and its three-way handshake
process. The surface-level process is fairly easy to understand. Pay close
attention to packet sequence numbers. They will definitely be an
exam item.IP Subnetting
So far we’ve established the basics through an overview of the OSI model layers and the
common network topologies. Let’s get a little deeper into the network layer and look at IP
addressing and its subnetting capabilities. Our goal here is to flex those subnetting muscles
and get our brains back to thinking about networking and its underlying nuances. Why?
Well, if you can subnet you can pinpoint a target and know how to go after it in the most
efficient and effective way.
Subnetting is the logical breakdown of a network address space into progressively
smaller subnetworks. That’s it. Stop thinking and take it for what it is! Now, as you break
down your address space into smaller subnetworks, you determine the numbers of network
bits and host bits by the requirements of your network. Network bits and host bits are
manipulated by the subnet mask. At this point I’m hoping you’re saying to yourself, “Oh
yeah, I remember this stuff.” If not, please dig into the details on your own. We are looking
at this topic in terms of how it will aid our effort as hackers.
Now that you grasp the basics of the subnet mask and how to use it to manipulate the
address space, you can see how knowing a few IP addresses can give you a clue as to how
an organization’s network is laid out. There’s more to come on this topic, but as a quick
example, knowing a single internal IP address can give a hacker much insight into the com-
pany’s addressing scheme.
You will be expected to know how to accomplish basic slash notation for
finding the broadcast address of specific subnets. Additionally, remember
the basic 127.0.0.1 for the local loopback address.Hexadecimal vs. Binary
Understanding hexadecimal and binary conversion is an important skill to have for the
exam. In the real world, for most network administrators conversion is done either by a
calculator or is not needed, but as an ethical hacker, you have opportunities to apply the
basic conversions to something useful. See Table 2.1 for the basic conversion between hex,
binary, and decimal.