Inroduction To IP Addressing - Part 2

By: Daniel Imbellino
Updated: Feb 28, 2013

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.

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.

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.

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

You are probably wondering why we are representing the IP addresses using the decimal system, when infact they’re binary values. This is because it’s easier for us 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. As you can see it is much easier to read decimal than binary. If you don’t know how the binary system works and would like to learn more about it, check out our comprehensive tutorials on the binary and hexadecimal systems under the main network tutorials page.