Introduction to IP Addressing

 Introduction to IP Addressing

IP (Internet Protocol) is the protocol we use to assign logical addresses to computers and networks across the internet for both public and private networks. Just as we have logical addresses (St Louis Mo 63139), and physical addresses (say 5400 N. Broadway), computers and networks too need an addressing scheme in order to function. Scenario: you write a letter, put a logical and physical address on an envelope, put the letter inside of the envelope, put a return address on the envelope, and then deliver the letter to your local post office to be mailed by the letter carriers. Networking works much the same way, and in this section we will discuss what the IP protocol is, how it works, and how to use it to your benefit when dealing with computer networking concepts.

IP addressing gives computers a way to assign addresses to your network or computer itself, and many of its functions rely on other protocols to make it function. One of these protocols is DNS (Domain Name System). DNS is a name to address resolution protocol, and here’s how it works: DNS matches a computer or networks logical address (IP Address) to a domain name. It would be ridiculous to try and remember the IP address of every website we want to visit, so it makes more sense to give networks a logical name along with its logical address to help as an identifier to that particular computer or network in question. Instead of typing in your address bar 145.15.10.0, it might be easier to just type Walgreens.com and have DNS do the work of finding the address for us, and this is exactly what DNS does. As soon as you type a domain name into Google search, Google then sends that request to a DNS server which then looks up that address in its data base. The DNS server then determines the logical address (IP Address) of the computer or network you are attempting to connect too, as well as the location (server) where the website resides, and then returns this information to you in the form of links that bring you to your destination.

There are two main IP addressing schemes in use today, they are IPV4 (IP Version 4), and IPV6 (IP Version 6). IPV4 uses a 32bit addressing scheme, while as IPV6 uses a 128bit addressing scheme. Being as IPV4 is still very much in use today, it makes sense for us to start our learning with this addressing scheme first.

An IPV4 address consists of a 32bit string of binary data that is separated into four separate octets (oct means 8). Each octet consists of 8 bits followed by a dot (.). One portion of an IP address is used to identify a network, and the other is used to identify the host (the computer system itself). This is known as dotted decimal notation, such as 192.168.1.2. Each octet can have a maximum value of 255 since there are 8 bits in each octet, and 28 = 256 (hence available values of 0 thru 255 = 256 possible values per octet). IP addresses are assigned into five major classes of network addressing as shown below.

The 5 major classes of IP addresses:

1.  Class A: The first octet identifies the network and the last 3 octets identify the host. Class A IP addresses have an available network range of 1 to 126. An example class A IP address could be 90.44.10.2. Class A addresses have a host range of 224 or approximately 16 million hosts per network. Class A addresses are the most limited and for this reason they are typically only assigned to very large organizations who can benefit from large host range it provides. Class A IP addresses that begin with 10 are considered private addresses. For instance, 10.140.14.1, this would be a private Class A address for use in internal networks only. When we state that the network range is from 1 to 126 we are referring to the value indicated in the first octet only! That being said, the fist octets value must be somewhere between 1 and 126.


2. Class B: The first 2 octets identify the network, and the last 2 octets identify the host. Class B IP addresses have a network address range of 128 thru 191. Ex: 140.18.10.5 (the first 2 octets identify the network address and last 2 the host). Class B IP addresses have an effective host range of 216 or 65,536 possible host addresses, this is because we are using 2 octets (that’s 16bits). These addresses are usually assigned to medium size organizations. Just as with the class A IP addressing scheme, the first octet of a class B IP address must be within the class B range of 128 thru 191. Class B addresses that start with the value 172.16 thru 172.31 are considered private network addresses for use in internal networks only.


3.  Class C: The 3 octets identify the network, and the last octet identifies the host. Class C IP addresses have a network range of 192 thru 223. Since class C IP addresses use the first 3 octets for the network address, they have the largest available pool of network addresses in use today, concerning IPV4. Class C addresses are typically assigned to medium sized organizations. The scheme also has an effective host addressing range of only 28 or 255 (that’s 0 to 255 or 256 possible values) since it uses only one octet for host addresses. Although technically speaking there are only 254 addresses available since you must count the “broadcast” address and network addresses, which we will talk about in a little bit here. Class C addresses that start with the value 192 are considered private network addresses for use in internal networks only. And, as before the 192 refers to the first octet only.


4. Class D: The class D addresses have been reserved for multicasting, which is the transmission of data packets to multiple destinations simultaneously. Video conferencing and streaming programs use this address range in order to transmit their data and make connections across the internet. The class D IP address range is from 224 thru 239, and just as with each other addressing scheme we just discussed, this value refers to the first octet only.


5.  Class E: This IP addressing scheme is not available to the public and is used for experimental use ( colleges, research, etc). It has an effective address range of 240 thru 255.

The address spaces allocated for private addresses:

Class A: 10 as in 10.90.14.2

Class B: 172.16 thru 172.31

Class C: 192 as in 192.168.2.1

Representing the IP addresses using the decimal system rather than original binary values. This is because it’s easier to read whole numbers rather than a long string of 1’s and 0’s. When manually assigning a network connection in windows you typically use standard decimal, which is then translated to binary for network and system use. For instance, let’s say you have the IP address 192.168.49.2 and you want to convert this to binary, the value obtained would be 11000000.10101000.00110001.00000010. It is much easier to read decimal than binary.