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. 194.66.170 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 (http://www.internic.net/) to ensure that all address attached to the Internet are uniquehttp://www.internic.net/

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

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 - 255.0.0.0  Class B - 255.255.0.0  Class C - 255.255.255.0  Example  192.5.5.35 255.255.255.224  192.5.5.35/27  You cannot skip bits!

14. Exercise 1. What are the two parts that make up an IP address? 2. What are the five classes of IP address, and which ones can be commercially used? 3. For an IPv4 IP address, how many bits are used and what is the total amount of addresses that can be derived? 4. What is the purpose of a subnet? 5. 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?