2.5. Identifying the Components and Structure of IP Addresses
In order to communicate effectively on a network, each device must be assigned a unique IP address. The IP address consists of two parts: a network address and a host address. You can think of the network address as a street name and the host address as a house on the street. As you can imagine, it would be very confusing for the mail carrier if multiple houses on the same street had the same number. In the same way, every host on a TCP/IP network must have a unique address for that network.
The IP addressing version that we use today is the same version that was developed in the early 1980s, IPv4. Since IPv4 offers more than 4 billion addressing possibilities, it was originally assumed that we would never run out of addresses (or that it would take a very, very long time). Because of the growth of the Internet and an inefficient use of IP addresses, we are in danger of running out of addresses in the not-too-distant future. Due to this fact, a new version of IP addressing, IPv6, is being developed. IPv6 will offer more than just an expanded number of possible addresses; it also promises improved security. In this section, we will discuss IPv4 and IPv6 in greater detail.
NOTE
For more information on IPv4 and IPv6, see Chapter 3 of the Network+ Study Guide, Fourth Edition.
2.5.1. Critical Information
You should know the components and structure of IPv4 and IPv6. In addition, you should know the required settings for connections across the Internet.
2.5.1.1. IPv4
IPv4 addressing is based on the binary system, which uses a series of ones and zeros to represent numbers and all other characters used by a computer. The reason that we have to use binary bits is that the computer only knows two states: on and off. (Actually, it only knows a fluctuation of voltage based on a timing signal.) With this method we can create numbers ranging from 0 to 255. This is the basis for all IP addressing as we know it today.
An IPv4 address (which we will refer to as an IP address from now on) is made up of four sets of 8 bits, called octets. Each bit in each octet has a value depending on its position in the octet. The leftmost bit of each octet has a value of 128, followed by 64, 32, 16, 8, 4, 2, and 1 as you move from left to right. Each bit can either be a 1 or a 0. If it is a 1, then its value counts based on its decimal value. If it is a 0, then its value does not count. Table 2.4 illustrates this method and creates the decimal value of 167 with binary bits.
You can facilitate communication of computers on your network or even on the Internet by configuring their active interfaces with the following:
| Bit Value | 128 | 64 | 32 | 16 | 8 | 4 | 2 | 1 | |
| Binary Digit | 1 | 0 | 1 | 0 | 0 | 1 | 1 | 1 | |
| 128 | +32 | +4 | +2 | +1 | =167 |
A valid IP address
An IP address that is unique and valid for the network or subnet in which it is configured.
A subnet mask
A 32-bit binary address, expressed in decimals, that defines which parts of the IP address refer to the network address and which parts refer to the host address.
A default gateway
The address of the inside interface of the router that is on your network or subnet and can give you access to or toward an Internet connection.
A DNS address
The address of a DNS server that can resolve requests and thereby provide access to Web information.
NOTE
We will discuss IP address configuration in greater depth later in this chapter.
2.5.1.2. IPv6
When IPv6 was first developed many experts thought we would be moving to it sooner than we have. Because of advancements in technology, which make network address translation easier and more prevalent in organizations, we have found ways to conserve the remaining IPv4 addresses and make more efficient use of them. We will, however, have to move to IPv6 addressing at some point in the future. In fact, the newest operating systems—Windows XP and Win-dows Server 2003—have the capability already.
The good news is, if we move to IPv6 within your lifetime, there is very little possibility that we will have to change again. This is because of the tremendous number of addresses that are available with IPv6. Whereas IPv4 is based on a 32-bit binary address, IPv6 will be based on a 128-bit hexadecimal address. This system will yield an astounding 340,282,366,920,938, 463,463,374,607,431,768,211,456 address possibilities.
IPv6 addresses will be expressed in a different format than IPv4. A 128-bit hexadecimal address is expressed as an 8-octet pair in hexadecimal separated by colons. The following is an example of an IPv6 address:
62CE:9D66:23FC:34D2:84CD:F5D1:9DC2:62CD
As you can see, hexadecimal addresses use only numbers and the letters A–F to express the values. This creates a system that has a tremendous number of possibilities. IPv6 will eventually provide greater numbers of addresses as well as enhanced security and traffic control, but it will require some re-education for those who use it. Like IPv4, a complete configuration for use of IPv6 on the Internet will require an IP address, subnet mask, default gateway, and a DNS server address.
2.5.2. Exam Essentials
Know the difference between IPv4 and IPv6. We are currently using IPv4, which is based on a 32-bit binary system. We will eventually move to IPv6, which is based on a 128-bit hexadecimal system.
Explain the requirements for connections on the Internet. Connecting to the Internet requires a valid IP address, subnet mask, default gateway, and an address of a DNS server.