Juan Murillo Consulting

Back Up Next

7 - IP Addressing - Part 1

One of the main purposes of “Computer Corner” is to eliminate the barriers that inhibit computer users from getting the most out their computers. One of these barriers is no doubt the amount of jargon that is tossed about when discussing computer operations and functions. To those who have not been educated along side computers, comprehending all the terminology in not unlike learning a second language.

Though there may be no way to avoid CSL (Computers as a Second Language), I will do my best to explain in lay terms the information I dispense. To that end, I have used the term “IP Address” a few times in past editions of Computer Corner but have not yet discussed how IP Addresses work or their significance in the world of technology today. So without any further ado, let’s demystify IP addressing once and for all. We’ll begin with a brief anatomy of IP addresses then move into their functions and types.

IP is an acronym for “Internet Protocol”; protocol being a fancy way of saying “language”. In previous editions I explained that computers communicate using a binary language consisting of “1’s” and “0’s”. A single 1 or 0 represents the smallest unit of computer information and is called a “bit”. Just as we humans group letters of the alphabet together to form words, computers form “words” by grouping eight bits together to form a “byte”. When referring to IP addresses, each byte is called an “octet” as it is comprised of eight independent values. Put four of these octets together and you have an IP Address.

A typical IP address in binary form might look something like this: “11011000.01101101.00101101.10011000”. Though this might make perfect sense to a computer, we humans have difficult time relating information in binary format. So, to make life easier for everyone, the computer industry has adopted the format of using the decimal or numeric value represented by each octet. Given that each bit in an octet has two possible values, 1 or 0, there are 256 unique combinations possible in each octet (28 or 2x2x2x2x2x2x2x2=256). These combinations range from “00000000”, with a decimal value of “0” to “11111111” with a decimal value of “255”. Therefore, each of the four octets in any IP Address can range from 0 to 255. Substituting the binary number in the preceding IP Address with its decimal equivalent yields an IP Address of: “” - obviously a much easier format for us humans to digest. (For more information on the binary language and how these decimal values are calculated see the April 18th, 2003 edition of Computer Corner - “The basics not so complicated”.)

IP Addresses are used as a means of identifying a device on a computer network. Whether the device is a Personal Computer (PC) on the Internet, or a printer in a corporate network, each device is assigned a unique IP Address that allows other devices to locate it for the purposes of sending and receiving information.

As such, IP Addresses function much like the postal address of your house or apartment. Just as the post office breaks down your home address into increasing levels of specificity from zip code, to state, to city, to street and finally to street number and possibly apartment number; computers use each octet of the IP Address to narrow the search for a computer device on a network.

In these terms, the first octet might represent the zip code. Using the example IP Address above, the devices zip code would be “216”. A computer searching for this device knows that it is “hosted” somewhere within the 216 network. The second and third octets might be thought of city and street, 109 and 45 respectively in our example. Finally, the last octet, 152, would be the street number, or in the case of a computer network the specific device being located or accessed.

There are several terms that you may hear associated with IP Addresses. “Public” and “private” for example, are used to describe the reach of an IP Address. The Internet Assigned Numbers Authority (IANA) has reserved three IP Address blocks for communications within private networks. These IP Addresses begin with “10.0”, “172.16” and “192.168”.

There are two principle reasons for the use of private IP addresses. The first is the availability of public IP Addresses. Considering that every device throughout the world must have a unique IP Address, the number of devices will soon outnumber the 4,294,967,296 unique IP Address combinations available (2 possible values, 1 or 0, in each bit, with 8 bits in each octet, times 4 octets -> 28x4 or 232 = 4,294,967,296).

The second but no less important consideration is security. Private IP addresses are not routable on the Internet, meaning that they can only be directly accessed by devices connected to the local network. This helps prevent “outsiders” from gaining access to computers or other devices on private networks.

Two other terms that come up often in IP address discussions are “static” and “dynamic”. Typically, these refer to how you computer is assigned an IP address. Static IP addresses are set manually on a device or computer and do not change until manually reconfigured. Dynamic IP addresses, on the other hand, are assigned by a DHCP server. DHCP is an acronym for “Dynamic Host Configuration Protocol”, or in layman’s terms, “He who assigns IP addresses”. In a DHCP environment, a device on a computer network maintains a database or “pool” of private IP addresses. When a computer or other device configured for DHCP connects to the network, the DHCP server assigns it the first available IP address in the pool automatically. Unless special options are configured on the DHCP server, there is no guarantee that a particular device will receive the same IP address each time it connects; hence the term dynamic IP address.

In the next edition we’ll discuss some examples of how IP addresses are used in home and corporate environments and provide some tools you can use to identify and test your IP address settings.

Back Up Next

Network Design &

Strategic Planning

Customer Relations

Project Management

Home & Home Office

Policies & Procedures


My Résumé

475 W. San Carlos Street, No. 9301 San Jose, CA 95110 •  E-mail