IP Tutorial 1. 2 An IP address is a unique number used to identify your computer on the internet. Every system has it’s own unique IP address. IP addresses

IP TutorialIP Tutorial 11

IP TutorialIP Tutorial


An IP address is a unique number An IP address is a unique number used to identify your computer on used to identify your computer on the internet. Every system has it’s the internet. Every system has it’s own unique IP address. IP addresses own unique IP address. IP addresses are layer 3, logical addresses.are layer 3, logical addresses.

IP AddressIP Address


IP StructureIP Structure

An IP address is made up of 32 bits. Each An IP address is made up of 32 bits. Each byte is represented by a decimal and byte is represented by a decimal and number separated by a full stop number separated by a full stop (period):(period):

207.21.32.101207.21.32.101


IP StructureIP Structure

Is an IP address, each value can never Is an IP address, each value can never be more than 255:be more than 255:

312.33.134.433312.33.134.433

Is an invalid IP address, the maximum for each byte is 255 (FF hexadecimal).


IP addresses are essential, they are used to IP addresses are essential, they are used to give your computer a unique identity. give your computer a unique identity. Without IP addresses routing would be Without IP addresses routing would be impossible. Say you send out a ping to a impossible. Say you send out a ping to a computer on a different network, your computer on a different network, your packets are sent to the router (gateway) on packets are sent to the router (gateway) on your network. The router checks the IP your network. The router checks the IP address in the packet headers, if the router address in the packet headers, if the router knows the network on which that IP is knows the network on which that IP is located, it forwards it on, if it doesn’t, it located, it forwards it on, if it doesn’t, it forwards it on to another router that might forwards it on to another router that might know where the IP address is. This know where the IP address is. This continues until the packet arrives at a continues until the packet arrives at a router that can forward it onto the router that can forward it onto the destination IP’s network, where it can then destination IP’s network, where it can then be picked up. Without IP addresses this be picked up. Without IP addresses this wouldn’t work.wouldn’t work.


IP addresses are separated into classes, IP addresses are separated into classes, let’s have a look at how they’re separated, let’s have a look at how they’re separated, then i’ll explain why:then i’ll explain why:

Range Range ClassClass0-1270-127 AA128-191128-191 BB192-223192-223 CC

IP Address ClassesIP Address Classes


Now to find out which class an IP address is in, you look at Now to find out which class an IP address is in, you look at the first byte of the address:the first byte of the address:

213.56.112.65213.56.112.65

The first byte is 213. This falls inside the class range 192-223 The first byte is 213. This falls inside the class range 192-223 making this a class making this a class CC IP address. IP address.

24.34.124.21324.34.124.213

The first byte is 24. This falls inside the class range 0-127 The first byte is 24. This falls inside the class range 0-127 making this a class making this a class AA IP address. IP address.

IP Address ClassesIP Address Classes


When I first read about IP addresses being split up When I first read about IP addresses being split up into classes, the author failed to explain why it was into classes, the author failed to explain why it was done, so i assumed this wasn’t very important, that done, so i assumed this wasn’t very important, that someone just put them into classes on a Sunday someone just put them into classes on a Sunday while they were bored or something. Take a look at while they were bored or something. Take a look at the table below:the table below:

RangeRange ClassClass N/HN/H0-1270-127 AA N.H.H.HN.H.H.H128-191128-191 BB N.N.H.HN.N.H.H192-223192-223 CC N.N.N.HN.N.N.H

Why?Why?


N = Network I.D and N = Network I.D and H = Host I.D. H = Host I.D.

In a class A IP address the first byte In a class A IP address the first byte is part of the network I.D. The is part of the network I.D. The remaining three bytes are part of the remaining three bytes are part of the host I.D. This means in class A there host I.D. This means in class A there can be fewer networks and many can be fewer networks and many hosts.hosts.

1.1. There can be 255 networks.There can be 255 networks.2.2. There can be 255 x 255 x 255 = There can be 255 x 255 x 255 =

16,581,375 theoretical hosts on each class 16,581,375 theoretical hosts on each class A network.A network.


In class B the first two bytes are part In class B the first two bytes are part of the network I.D and the remaining of the network I.D and the remaining two are part of the host I.D. This two are part of the host I.D. This means in class B there can be a means in class B there can be a reasonable amount of networks, and reasonable amount of networks, and a reasonable amount of hosts on a reasonable amount of hosts on each one of those networks.each one of those networks.

1.1. 255 x 255 = 65,025 networks.255 x 255 = 65,025 networks.2.2. 255 x 255 = 65,025 theoretical hosts on 255 x 255 = 65,025 theoretical hosts on

each of those networks.each of those networks.


I’m sure you get the drift, class C:I’m sure you get the drift, class C:

255 x 255 x 255 = 16,581,375 255 x 255 x 255 = 16,581,375 networks.networks.

255 theoretical hosts on each of those 255 theoretical hosts on each of those networks.networks.


I say “theoretical” hosts on each class of I say “theoretical” hosts on each class of network, because on each network the network, because on each network the first address and the last address cannot first address and the last address cannot be used. So if you work out the theoretical be used. So if you work out the theoretical number of hosts then take away two you number of hosts then take away two you have the actual number of host computers have the actual number of host computers that can be on that same network.that can be on that same network...

Why Theoretical?Why Theoretical?


IP Address: IP Address: 213.54.112.221213.54.112.221

This is a class C address.This is a class C address.213.54.112.0 213.54.112.0

is the NETWORK address. This cannot be is the NETWORK address. This cannot be used as a hosts IP address.used as a hosts IP address.

213.54.112.255 213.54.112.255 is the BROADCAST address on this network. is the BROADCAST address on this network.

It cannot be used as a hosts IP address.It cannot be used as a hosts IP address.

Class C networks have a theoretical 255 Class C networks have a theoretical 255 hosts on each network, 255 – 2 = 253. So hosts on each network, 255 – 2 = 253. So on each class C network you can have 253 on each class C network you can have 253 host computers.host computers.


Let’s go over a couple of examples Let’s go over a couple of examples to make this stick. What is the IP to make this stick. What is the IP Class, Network ID, Network Class, Network ID, Network Broadcast Address and the Number Broadcast Address and the Number of Hosts on the Network of the of Hosts on the Network of the following IP Addressesfollowing IP Addresses

IP: 203.222.34.57IP: 203.222.34.57..

IP: 24.240.11.99IP: 24.240.11.99


Is a class C address, N.N.N.HIs a class C address, N.N.N.H

The network ID is 203.222.34.0The network ID is 203.222.34.0

The network broadcast address is 203.222.34.255The network broadcast address is 203.222.34.255

There can be 255 Theoretical hosts on this There can be 255 Theoretical hosts on this network.network.

Thus there can be 255 – 2 = 253 host Thus there can be 255 – 2 = 253 host computers functioning on this network.computers functioning on this network.

IP: 203.222.34.57IP: 203.222.34.57


Is a class A address, N.H.H.HIs a class A address, N.H.H.H

The network ID is 24.0The network ID is 24.0

The network broadcast address is The network broadcast address is 24.255.255.25524.255.255.255

There can be 255×255 x 255 = 16,581,375 There can be 255×255 x 255 = 16,581,375 Theoretical hosts on this network.Theoretical hosts on this network.

Thus there can be 16,581,375 – 2 = 16,581,373 Thus there can be 16,581,375 – 2 = 16,581,373 host computers functioning on this network.host computers functioning on this network.

IP: 24.240.11.99IP: 24.240.11.99


Try applying the above to your IP Try applying the above to your IP address, what class network are you address, what class network are you on? What’s the network I.D? What’s on? What’s the network I.D? What’s the broadcast address? How many the broadcast address? How many hosts can be on your network?hosts can be on your network?

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IP Tutorial 1. 2 An IP address is a unique number used to identify your computer on the internet. Every system has it’s own unique IP address. IP addresses