1. Introduction to networking (Yarnfield)
IP addresses

2. Objectives Define an IP address Describe IP address classes
Describe network and host portions of an address
Describe what a broadcast address is used for
Describe what private IP addresses are used for

3. The Internet Protocol Every machine MUST have a unique address
This is referred to as the IP address
This address is used to route packets of information using TCP/IP to a specific machine
The address is made up of two parts a network address and a host address
To find your IP address type ‘ipconfig’ into a command line window

4. The network part of the address
Is used to route the packet to the correct network
i.e would direct the packet to one part of the Staffordshire university network
Once the packet is within the network
The host part of the IP address is important to direct the packet to actual machine within that network
The network address size changes depending on the size of network in which the host is connected.
Class A, B, and C
All network addresses are issued by InterNIC ( to ensure that all address attached to the Internet are unique

5. Host addresses

6. Address representation (IP v4)
An IP address is a 32 bit value
In theory this gives over 4 billion possible addresses
In reality the actual number of available addresses is a lot less than this
An IP address is represented by dotted decimal numbers
In reality within the network the values are represented by binary
As humans we do not use binary, as these are difficult for us to remember
Also it is very easy with a large number sequence to make mistakes when setting the IP address

7. Address classes
Address 127.*.*.* is a reserved address to indicate loop back
i.e. communicate with the device sending the request

8. Address classes

9. Address classes

10. Broadcast address
Is an IP address which is used when communications are required with ALL of the devices with a certain network address
This value is 255 in the host part of the address

11. Private IP addresses
A number of IP addresses have been reserved for private use on local LANS
If you setup a Microsoft windows network it will default to a class C private network IP address

12. Subnets
Subnets allow for a host part of a host address to indicate a subnet
These are smaller local networks within the major network
The advantage is that this allows a packet to be more tightly direct to a host
The disadvantage is valuable host addresses are used to create a subnet
More details about subnets will be given during the course

13. Subnet address Also 32 bits in length
Indicates which part of the IP address is the network, and which part is the host
Each class has a default subnet mask
Class A
Class B
Class C
Example
/27
You cannot skip bits!

14. Exercise What are the two parts that make up an IP address?
What are the five classes of IP address, and which ones can be commercially used?
For an IPv4 IP address, how many bits are used and what is the total amount of addresses that can be derived?
What is the purpose of a subnet?
What will a broadcast IP address actually do?

15. Summary
IP addresses are used to route packets of data throughout a network
IPv4 uses 32 bits
Hierarchical in nature
Classes are A, B, C, D and E
Classes A, B and C are used commercially
Broadcast addresses reach all host machines on a network

16. Questions...
...are there any?