Relative Content

IP addresses

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 – the classful subnet mask is /8. The number of possible IP addresses is 16,777,216 (2 to the power of 24).Class B – the classful Read more […]

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 of 1s in the subnet mask. With 1 subnet bit, we can have 21 or 2 subnets. With 2 bits, 22 or 4 subnets, with 3 bits, 23 or 8 subnets, etc.2. How many hosts per subnet do we need?2y – 2 = number Read more […]

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, What does it mean? Well, like an IP address, a subnet mask also consists of 32 bits. Computers use it to determine the network part and the host part of an address. The 1s in the subnet mask Read more […]

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 has the following disadvantages:a single broadcast domain – all hosts are in the same broadcast domain. A broadcast sent by any device on the network will Read more […]

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 for other purposes – class D for multicast and class E for experimental purposes.The system of IP address classes was developed for the purpose of Internet IP addresses assignment. The classes created were based Read more […]

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, according to its needs. But there was one huge problem with this concept – if each host on each network in the world was provided with an unique IP address, we would have Read more […]

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 can see that the host wants to communicate with the server. It uses the (unicast) IP address of the server ( to do so.2. multicast IP addresses Read more […]