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IP Addressing (IPv4)

Category: IP, IPv4, Routing
Author: gokhankosem, on 24 Oct 17 - 0 Comments
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IP Addressing (IPv4)

IP Addressing is one of the key point that a network engineer need to learn first. In this article we will start with the distribution of the IP addresses and we will see all the details of IP Addressing. Here, we will mainly focus on IPv4 Addressing. IPv6 Addressing is also explained in another lesson.

Let’s start with the dsitribution of IP Addresses and see that where is this valuable numbers are coming to us…

How Does IP Addresses are Controlled?

IP addresses are controlled and distributed by IANA (Internet Assigned Numbers Authority). This authority gives the IP addresses to the Ragional Internet Registries (RIRs) and they distribute to the area or continental that it is responsible for.

There are 5 different Ragional Internet Registries (RIRs) in the world. These RIRs are:

RIPE NCC (Réseaux IP Européens Network Coordination Centre)
APNIC (Asia-Pacific Network Information Centre)
AFRINIC (African Network Information Centre)
ARIN (American Registry for Internet Numbers)
LACNIC (Latin American and Caribbean Internet Addresses Registry)


There are currently two versions of IP Addresses. These are:

• IPv4
• IPv6

As we said before, in this lesson, we will focus on IPv4. IPv6 is explained in another lesson series.

IPv4 Addresses

IPv4 Addresses are 32 bits (8 bytes) addresses. This addresses are showed with four decimal numbers that are divided with dots like

Here, all the decimal numbers can be from 0 to 255. This is basic math. If you have 8 bits for each number, you can produce number from 0 to 255.

We will talk about this detaily in this lesson.

IP Addresses are consist of two parts. The first part is network part and the second part is host part. This is detereined accourding to Subnet Mask.

Subnet Mask is also a number series like IP address, that shows the network portion of an IP address. Subnet Masks are used together with IP addresses.Subnet Mask can be like As binary, this is 11111111.11111111.11111111.00000000.Here, 1’s are representing the network side. 0’s are representing host side.
Without Subnet Mask, we can not know that which network is this IP address belong. We will talk about this with Subnetting detailly.

Let’s show this with the IP address For example we will use the Subnet Mask This subnet mask’s binary written is like 11111111.11111111.11111111.00000000. It is saying that, the first 3 octet (first 24 bits) shows the network part. Because it is full of 1s. The last octet is full of 0s. And show hosts. 1s are for network and 0s are for host devices in this network.

So, in the last case, we can say that all the devices in this network will use the same network part (192.168.2).

But host part can change from 0 to 255 like below:


• The first address is the network address.
• The last address is the broadcast address.
• The other addresses from to can be used for a device in the same network.

IP Address Classes

IP Addresses are divided into different Classes at the beginning. For different sized networks, different IP Address Class is used.These IP Address Classes has strict borders. This is calles Classful IP Addressing. With subnetting, this is not important anymore.

What are these IP Address Classes and IP Address ranges? These are:

• Class A ( to )
• Class B ( to )
• Class C ( to )
• Class D ( to )
• Class E ( to )

The network and host parts of these networks are:

• Class A has 126 networks (The first octet) . The rest is used for hosts.
• Class B has 16 384 networks (First and second octets) . The rest is used for hosts.
• Class C has 2 097 152 networks(First, Second and Third octets). The rest is used for hosts.
• Class D is used for Multicast operations.
• Class E is reserved Class.

Here,, and addresses are reserved for various roles. These reserved address roles are:

• – Used for Default Routes
• – Used for Loopback
• – Used for Broadcast

This classless IP address is only a theorical information for you. In real word you can not see this classes.
Let’s talk about the real classes or IP address types. These IP address types are:

• Private IP Addresses
• Public IP Addresses

Private IP Addresses are the IP addresses that used in local networks. These IP addresses are not routable in the internet. So, different companies, home networks etc. can use these Private Block IP Addresses in their local network. These Private Block IP Addresses are:

• to
• to
• to


The local devices in a network uses this Private Block IP addresses and with NAT, they are translated to a routable addresses at the Gateway. Then, the local devices can use Internet.

Public IP Addresses are unique IP addresses used on Internet. They are assigned by IANA to Regional Internet Registries (RIRs). And then RIRs distribute this to the companies that need IP addresses. The other IP blocks except Private Blocks, Multicast Blocks and Reserved Blocks are all in Public IP Address Blocks.

By the way, there is also another reserved block. This is the IP addresses from to This reserved IP addresses are used for Automatic Private Addressing. This is used in your PC if it did not get an IP address from the Home Router or DHCP Server.

IP Address Types According to Delivery Type

Now, let’s talk about the IP addresses according to delivery type. We can divide IP addresses into four according to delivery type. These are:

• Unicast Address
• Broadcast Address
• Multicast Address
• Anycast Address

Now, let’s see what are these IP addresses.

• Unicast Address is the address that represents one host.
• Broadcast Address is the address that representrs all the hosts in the network.
• Multicast Address is the address that represents member of a specific group in a network.
• Anycast Address is not represents a specific device IP. But, it is used with other devices and provide the delivery to the nearest one by help of Routing Protocols.

=> IPv4 support these IP types except Anycast Address. There is no Anycast IP Address in IPv4.

=> IPv6 support these IP types except Broadcast Addres. There is no Broadcast Address in IPv6.

For the Other Parts of these article series, you can check the below lessons :

IPv4 – IP and Layer 3 Overview
IPv4 – IP Addressing
IPv4 – Subnetting and Subnetting examples
IPv4 – Home Internet Connection Basics

Fot IPv6 Addressing, you can check the below lessons :

IPv6 – Part 1 (IPv6 and IPv6 Addresses)
IPv6 – Part 2 (What does IPv6 bring?)
IPv6 – Part 3 (Address Types in IPv6)
IPv6 – Part 4 (Subnetting IPv6)

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About the Author
Gokhan Kosem is a telecommunation and network engineer. His ambition to IP networks and end-to-end system installation made him to prepare this web-site. By sharing his experiences about various networking protocols beside different system installation experiences and Cisco, Juniper, Alcatel-Lucent devices configurations, he is aimed to be helpful for his collegues in all over the world. He is currently lives in Istanbul, Turkey.

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