The following is a summary of each topic in the chapter and some questions for your reflection.

What Did I Learn in this Module? (20.3.1)

• Binary Number Systems—Binary is a numbering system that consists of the digits 0 and 1 called bits. In contrast, the decimal numbering system consists of 10 digits consisting of the digits 0 – 9. Hosts, servers, and network devices use binary addressing. Specifically, they use binary IPv4 addresses. For ease of use by people, IPv4 addresses are commonly expressed in dotted decimal notation.

This decimal system uses the powers of ten, or base 10. For example, the number 2,146 has a 2 in the thousands place, or two thousand. 2,146 has a 1 in the hundreds place, or one hundred. It has a 4 in the tens place, or forty. It has a 6 in the ones place, or six.

The binary system is a base 2 number system. Each place value can have a 0 or a 1. A useful tool is the binary positional value table. It is common to use a table with eight placeholders. 8 bits equal a byte.

• Hexadecimal Number System—The hexadecimal numbering system is used in networking to represent IP Version 6 addresses and Ethernet MAC addresses. This base sixteen number system uses the digits 0 to 9 and the letters A to F. Binary and hexadecimal work well together because it is easier to express a value as a single hexadecimal digit than as four binary bits.

IPv6 addresses are 128 bits in length and every 4 bits is represented by a single hexadecimal digit; for a total of 32 hexadecimal values. IPv6 addresses are not case-sensitive and can be written in either lowercase or uppercase.

• Reflection Questions (20.3.2)—I wasn’t expecting to do math in the middle of my networking course, but I was surprised by how much fun it is to convert decimal numbers into their binary and hexadecimal equivalents. I have a better understanding of why IP addresses are represented the way that we see them. Before you took this module, what did you know about binary and hexadecimal numbering systems? Take a look at the MAC Address on your computer’s NIC. What do you recognize about this address that you may not have before?