CIDR (Classless inter-domain routing)

CIDR (Classless inter-domain routing) is a method of public IP address assignment. It was introduced in 1993 by Internet Engineering Task Force with the following goals:to deal with the IPv4 address exhaustion problemto slow down the growth of routing tables on Internet routersBefore CIDR, public IP addresses were assigned based on the class boundaries:Class A […]

Create subnets

There are a couple of ways to create subnets. In this article we will subnet a class C address that, by default, has 24 subnet bits and 8 host bits.Before we start subnetting, we have to ask ourselves these two questions:1. How many subnets do we need?2x = number of subnets. x is the number […]

Subnet mask

An IP address is divided into two parts: network and host parts. For example, an IP class A address consists of 8 bits identifying the network and 24 bits identifying the host. This is because the default subnet mask for a class A IP address is 8 bits long. (or, written in dotted decimal notation, […]

Subnetting explained

Subnetting is the practice of dividing a network into two or more smaller networks. It increases routing efficiency, enhances the security of the network and reduces the size of the broadcast domain.Consider the following example:In the picture above we have one huge network: All hosts on the network are in the same subnet, which […]

Classes of IP addresses

TCP/IP defines five classes of IP addresses: class A, B, C, D, and E. Each class has a range of valid IP addresses. The value of the first octet determines the class. IP addresses from the first three classes (A, B and C) can be used for host addresses. The other two classes are used […]

Private IP addresses explained

The original design of the Internet intended that each host on every network should have a real, routable IP address. An organization that would like to access the Internet would complete some paperwork to describe its internal network and the number of hosts on it. The organization would then receive a number of IP addresses, […]

Types of IP addresses

The IP addresses are divided into three different types, based on their operational characteristics:1. unicast IP addresses – an address of a single interface. The IP addresses of this type are used for one-to-one communication. Unicast IP addresses are used to direct packets to a specific host. Here is an example:In the picture above you […]