LESSON 1

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:


unicast ip address
Unicast IP address example

In the picture above you can see that the host wants to communicate with the server. It uses the IP address of the server (192.168.0.150) to do so.

2. Multicast IP Addresses – used for one-to-many communication. Multicast messages are sent to IP multicast group addresses. Routers forward copies of the packet out to every interface that has hosts subscribed to that group address. Only the hosts that need to receive the message will process the packets. All other hosts on the LAN will disard them. Here is an example:


muticast ip address
Multicast IP address example

R1 has sent a multicast packet destined for 224.0.0.9. This is an RIPv2 packet, and only routers on the network should read it. R2 will receive the packet and read it. All other hosts on the LAN will discard the packet.

3. Broadcast IP Addresses – used to send data to all possible destinations in the broadcast domain (the one-to-everybody communication). The broadcast address for a network has all host bits on. For example, for the network 192.168.30.0 255.255.255.0 the broadcast address would be 192.168.0.255. Also, the IP address of all 1’s (255.255.255.255) can be used for local broadcast. Here’s an example:


broadcast IP address
Broadcast IP address example

R1 has sent a broadcast packet to the broadcast IP address 192.168.30.255. All hosts in the same broadcast domain will receive and process the packet.

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).

Classes of IP addresses:


Classes of IP address
Classes of IP address

Special IP Address Ranges: – Addresses used to communicate with the current network

127.0.0.0/8 – Loopback Addresses

169.254.0.0/16 – Link-Local Addresses (APIPA)

LESSON 2

Subnetting Explained

Subnetting- It 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:


Sub netting
Subnetting example

In the picture above we have one huge network: 10.0.0.0/24. All hosts on the network are in the same subnet, which has following disadvantages:

A Single Broadcast Domain – All hosts are in the same broadcast domain. A broadcast sent by a device on the network will be processed by all hosts.

network security – Each device can reach any other device on the subnet, which can present security problems.

Organizational Problems – in a large networks, different departments are usually grouped into different subnets. For example, you can group all devices from the Accounting department in the same subnet and then give access to sensitive financial data only to hosts from that subnet.

The network above could be subnetted like this:


Subnetting example 2
Subnetting example 2

Now, two subnets were created for different departments: 10.0.0.0/24 for Accounting and 10.1.0.0/24 for Marketing. Devices in each subnet are now in a different broadcast domain.