In this section I will look at IP version
4 address. Even though I P version 6 networking is available and is starting to be used, I
P version 4 networking will still be around for a long time to come.
In this video I will first look at what is IP version 4 followed by what is an IP version
4 address. It is important to understand what makes up an IP version 4 address. When IP
version 4 was first developed they introduced the concept of classfull networking. Even
though this concept has become depreciated over the years, it is still important to understand
how it works to have an understanding of IP version 4.
Next I will look at the process of subnetting. Subnetting is taking a large network and dividing
it up into smaller parts. Finally I will have a look at private addresses. Private addresses
are IP addresses that you can allocate how you see fit inside your organization.
I P version 4 is the fourth version of the IP protocol. It is the default protocol for
the internet and by far the most popular protocol in use today. Version 5 of the I P protocol
never got adopted on the internet, however IP version 6 is starting to be used. Even
so, IP version 4 will be in use for a long time to come and thus it is important that
you have a good understand of the protocol. To understand how IP version 4 protocol works
consider this. The IP and the TCP protocol combine together to provide a complete network
solution. TCP is responsible for keeping messages in order and retransmission data when lost
while the IP part is simply responsible for sending packets from one location to anther.
IP version 4 addresses are 32 bits long. They are divided into 4 octets of 8 bits separated
by dots to make reading easier. For example 192.168.0.1. An IP address identifies your
computer and allows other computers to contact yours. Think of it like a telephone number.
Telephone numbers have areas codes while IP addresses have network ID’s to help separate
and organise your network into logical parts. Originally all networking was divided into
classes. These classes when from a to e and depending on the class determined how many
computers could be on that network. These networks can be broken down into smaller
parts in a process called subnetting. IP version 4 since it was originally introduced has been
improved and developed. The system of classes put limits on the way networks could be designed.
Since than classless networks have been added which allow you to change the way networks
are designed. They introduce a system called supernetting which allows you to combined
multIPle networks together. I will go through all of these features individually, but first
lets start with class networks otherwise known as classful networking.
Originally all IP addresses were allocated based on a class. The class used determines
the number of hosts that can be deployed on that network. Today classless networks have
become more common which I will cover later. The remnants of classful networking still
exist today and often use in the discussion of networking so it is important topic to
know. The first class, class a supports 16,777,214
hosts. These are available in 126 networks. The network and host ID can not be all zeros.
The 127 network is reversed for loopback. If you ping any addresses in the 127 network
you are pinging your local computer. This is using for testing. The last host ID, or
a host ID with all 1’s is reversed for broadcast. The next class is called class B. This class
has 16,384 networks and 65534 host per network. As you can see both class A and class B have
a lot of hosts per network. The original system of allocating IP addresses based on class
created a lot of wasted IP addresses. The class C network has 2,097,152 networks
with 254 hosts per network. This network is more suitable for smaller networks, however
you can see that even if you have 100 computers on a network there is still a lot of wasted
IP addresses. Class D is reversed for multicast. Multicast
allows you to send one packet to many computers. The last class is class E. This class is reversed
and not currently in used. Using classful networking by itself creates a lot of wasted
IP addresses. In order to use the address space better you can use subneting.
Subnetting allows you to break up a network into smaller parts. It is also used to determine
which traffic is local traffic and which traffic is for a remote network. Unfortunately once
you start subnetting your network you will need to start working in binary. To see how
subneting works consider this example. As you can see the IP address, subnet mask and
destination IP address are displayed in binary. When the subnet mask is shown in binary you
can see that it is a unbroken list of ones followed by zeros. Ones must always be on
the left and zero’s on the right. Because of this you can represent the subnet by the
IP address slash number of bits. If I was to show this IP address and subnet mask shown
in the example using slash notation it would be 192 dot 168 dot 10 dot100 slash 24 as there
are 24 one bits in the subnet mask. The subnet mask is used to determine if the
traffic is for a remote network or the local network. To do this, the bits from the IP
address and the destination address are compared but only with reference to the subnet mask.
In this example, the subnet mask is 24 bits so the first 24 bits of the IP address and
the destination IP address are compared. If they match, which in this case they do, the
packet is sent to the local network. Now you may be thinking, I could just look
at the first 3 octects of the IP address and the destination IP address to see if they
match. The answer is you could in this case because the subnet mask is a simple one. The
idea behind subnetting is you can take a larger network and make it a smaller network.
If I were to change the subnet mask as follows. The subnet is no longer as simple to work
out. By using this subnet I now have divided my original network into 14 smaller networks
which I can put 14 hosts per network in each network.
In other words I have allocated 4 bits of the host part of the address to the network
part of the IP address. If you take the same IP address and the same destination address
again and compare the subnet mask against the IP address and destination address you
get the following. You can see that the first 4 bits in the last
octect do not match. Since they do not match this packet is not for the local network and
will be sent to the default gateway. As you can see, subnetting gives you a lot of flexible
and power to break down larger networks into smaller ones. The trade off is that you need
to start doing some binary operations. Using subnetting you can break away from the
limits imposed by classful addresses and divide a network up any way you want. This is called
classless inter domain routing. The subnet masked used is called variable length subnet
masking. In the real world, classless inter domain routing is the primary method used
and classfull networks are a thing of the past. It is important to know about classfull
network as they are often referenced in literacy and the real world.
Classless inter domain routers uses a different way to indicate the subnet mask. To indicate
the number of bits in the subnet it uses a slash subnet mask as shown in these examples.
The number indicated after the slash indicates the number of bits in the subnet mask.
Using classless inter domain routing you can also perform what is called supernetting.
Super netting combines multIPle network together to form a larger network. If you had the networks
192.168.0.0 to 192.168.3.0 this would be 4 class c networks with 254 hosts in each network.
If you needed a larger network you could combine the networking into one using super netting.
By using the subet mask 22 you can combine the 4 networks in one. This will give you
one network with 1022 hosts. As you can see once you start using classless inter domain
routing the IP address space can be divided up any way that you want without any of the
limits imposed by classful networking. In the IP address space, there are a number
of addresses reserved for private use. These address you are free to allocate anyway you
want. These addresses are not routable on the internet. A lot of companies use this
fact to help with their security. If you place all your computers on a private network a
would be hacker on the internet can not connect to any of your computers directly. This is
because there is no routing from their computer to your computers.
There are 3 groups of private addresses. The first is class a which goes from 10.0.0.0
to 10.255.255.254. The next is class b from 127.16.0.0 to 172.31.255.254 and lastly class
C, 192.168.0.0 to 192.168.255.254. All these addresses you are free to use anyway that
you want and route them in your organisation any way that you want. Just remember that
they are not routable on the internet. On the topic of private addresses, if you
start using them you should be aware of the Automatic private IP address system. This
system is used by windows when windows can not contact a dhcp to get an IP address.
When this occurs, windows will allocate a random IP address from the network 169 dot
254 dot 0 dot 0. This allows the computer to communicate on a local network. The idea
of this system is that you could connect a computer up at home to a switch with one or
more computer connected to the same switch. The computers will automatically allocate
an IP address using Automatic private IP address and be able to communicate with each other.
Remember however these addresses are not routable on the internet. If you decide to use private
address ranges on your network, bare in mind that you should avoid using this range otherwise
you may gets some unexpected results. Look out for IP addresses in this range. When
troubleshooting if you get an address in this range will mean that the computer is having
trouble accessing the DHCp server. Once you have decided on your network address
and subnet masks, there are two more special addresses that you should be made aware of.
For example if I take the following IP address and subnet mask. This would translate to the
following subnet in binary and the following IP address in binary.
You will notice that the host part of the IP address shown in red in all zeros. This
address is not valid and can’t be used. This is often used as the network ID. The
other address that is not valid is when the host part of the IP address is all ones.
For example the following IP address , if I again look a the subnet in binary and than
compare it to the IP address in binary, you will notice the host part of the IP address
is all ones. This kind of IP address is used for broadcast.
If you want to sent data to all computers on a network sent it to this address. It is
also possible to sent a broadcast from anther network to this address. You will however
find that a broadcast like this will often be blocked by the router to that network.
This is done as broadcast like these have been used in denial of service attacks.
When working out the subnets for you network and how many hosts you will have, the usable
amount of IP addresses can be worked out using the formula 2 the power of hosts bits minus
2. If I take the previous example. 2 to the power of 10 minus 2 gives us 1022 usable hosts.
When dividing your networks into smaller parts using subnetting, make sure you factor in
some growth for your network otherwise you may find that your network will become full.
Remember with IP version 4, even though it has been around since the 70’s, it has been
developed and improved since than and will be around for a long time to come. It is costly
for a company to change it’s networking over to IP version 6 and with out a driving
need and a lot of people will stay on IP version 4 for a long time to come.
Also a lot of network equIPment, even though support for IP version 6 is growing, still
only support IP version 4. If you are planning to use private addresses, remember that they
are not routable on the internet. Lastly when setting up your network plan for growth. Networks
can often expand a lot larger than they were originally envisioned.
You may think you have enough space now, but think about if you company decided to give
everyone an IP based phone or a had a major expansion. In short, IP version 4 is not here
to stay, but will be here for a long time so it is worth the time to learn.