Unit 24 Network Design and Administration IP Addressing (Pt.1)

IP addressing: Objectives To examine data sharing on computer networks To outline the different network protocols used in todays computer networks To understand the nature of IP addressing, classes of IP address To understand the importance of subnet masks and subnetting

How do Computers Share data? How is information and data passed around networks? (LANs and WANs) How does an reach its destination? How do you access the Internet and download a web site? How does your word document reach the printer?

The Beginning When was the Internet created? Why was it created? When was the World Wide Web created? Why was it created? Vint Cerf and Robert Khan in 1972, were given the task of finding a networking protocol that would allow effective communication between the next generation of ARPANET computers

Intro to IP addressing Vinton (Vint) Cerf, along with a group of Stanford University graduates, in December 1974, designed a networking protocol which included a 32 bit IP address, with eight bits for identification of a network, and 24 bits for identification of a computer, which provided support for up to 256 networks, each with up to 16,777,216 unique network addresses. It was assumed that the network design would eventually be re-engineered for a production system, but the architecture proved remarkably robust. Cerf has said that once the network was developed and deployed, it just "continued to spread without stopping!"

Introduction – What is an IP Address? Every machine with access to the Internet has a unique identifying number, called an Internet Protocol (IP) Address. A typical IP address looks like this: To make it easier for humans to remember, IP addresses are normally expressed in decimal format as a "dotted decimal number (and then as a name using DNS) But computers communicate in binary form. Look at the same IP address in binary:

IP Addresses IP addresses are considered 32-bit numbers The four numbers in an IP address are called octets, because they each have eight positions when viewed in binary form. Each octet can contain any value between 0 and 255, but only certain values can be allocated as routable IP addresses (explained later)

IP Addresses How do you convert a Binary number to a decimal number? Take the binary number What is the smallest and largest numbers that can be represented by 8 bits?

Classes of IP Address The octets serve a purpose other than simply separating the numbers. They are used to create classes of IP addresses (IP version 4) that can be assigned to a particular business, government or other organisation based on size and need. The octets are split into two sections: Net and Host. The Network section always contains the first octet. It is used to identify the network that a computer belongs to. Host (sometimes referred to as Node) identifies the actual computer on the network. The Host section always contains the last octet

Class A IP Addresses This class is for very large networks, such as a major international company might have. IP addresses with a first octet from 1 to 126 are part of this class. E.g The other three octets are used to identify each host. This means that there are 126 Class A networks each with 16,777,216 possible hosts Class A networks account for half of the total available IP addresses.

Class A IP Addresses 16,777,214 possible hosts/computers on a network Note: The Network ID for a class A network is the first octet followed by 3 zeros E.g

Class B IP Addresses Used for medium-sized networks. A good example is a large college campus. IP addresses with a first octet from 128 to 191 are part of this class. E.g Class B addresses also include the second octet as part of the Net identifier. The other two octets are used to identify each host. This means that there are 16,384 Class B networks each with 65,536 possible hosts/computers Class B networks make up a quarter of the total available IP addresses.

Class B IP Addresses 65,534 possible hosts /computers on this network Note: The Network ID for a class B network is the first 2 octets followed by 2 zeros E.g

Class C IP Addresses Class C addresses are commonly used for small to mid-size businesses. IP addresses with a first octet from 192 to 223 are part of this class. E.g Class C addresses also include the second and third octets as part of the Net identifier. The last octet is used to identify each host. This means that there are 2,097,152 Class C networks each with 254 possible hosts/computers Class C networks make up an eighth of the total available IP addresses.

Class C IP Addresses 254 possible hosts / computers Note: The Network ID for a class C network is the first 3 octets followed by 1 zero E.g

Example – A simple LAN A Class C IP addressing system using 4 computers

IP Address Determination IP Address class IP AddressNetwork ID Range of values of w A w.x.y.z w B w.x.y.z w.x C w.x.y.z w.x.y D w.x.y.z Not available E w.x.y.z Not available

Private IP Addresses A network manager / administrator can allocate IP addresses as they see fit – there are no real rules when routing data around private networks, although all administrators must still allocate addresses according to the classes of IP address and appropriate subnet masks. There are 3 main IP addresses that are always used for private networks, and are never routed to the Internet (hosts from to ) (hosts from to (hosts from to ) (Automatic Private IP Addressing – APIPA)

IP addresses you cannot assign ValueWhy not? 127This is an internal IP address to test for connectivity and IP prevalence 255Used as a Broadcast address Used as a Multicast address For future use Internal Microsoft address used as an emergency address

Subnetting and Subnet Masks IP routing protocols can be extended still further by the use of subnet masks. A subnet mask is used for 2 main purposes 1. To allow further expansion to an existing network, by allowing additional segments to be added to a LAN. This allows other physical devices to be added 2. To define the type of network (whether class A, B or C)

Subnet Masks Lets assume we have an IP address of: This is a Class C address (192) therefore the network ID is And the address of the specific machine is.5 The subnet mask for this address would be: Therefore the subnet mask identifies this IP address as a Class C IP address

Subnet Mask Examples Class AClass C Class B

Subnet Mask Examples

What is the Subnet Mask? A Class B IP addressing system using 4 computers

The College Network Bury College has over 1600 computers, laptops, servers etc spanned across 4 sites, Woodbury, Millennium, Prospects and Peel. Due to the number of hosts / computers, what class of IP address does the college need? A Class B IP Address – with the facility for 65,384 hosts What will the subnet mask be?

Using Subnet Masks: Bury College Woodbury Centre IP Address Millennium Centre IP Address Subnet Mask:

The College Network IP addresses can be allocated in 2 ways Statically and Dynamically Devices such as Printers are allocated a static IP address so that all computers on the network can find them all of the time, without the need for re-mapping Most computers on the Internet and within large LANs allocate IP addresses dynamically

The College Network Using DHCP (Dynamic Host Configuration Protocol) each time someone logs onto a client computer, the server allocates that computer an IP address, but it may not be the same address each time. The address allocated will fall into the range of the Class B address the college has: E.g

Example of IP and Subnet at Bury College

In Summary: InterNIC, under the authority of the Internet Assigned Numbers Authority (IANA), allocates the network portions of IP addresses to Internet Service Providers (ISPs) ISPs and LAN managers are responsible for assigning the host portion of the IP address to machines within their local networks. (maybe by using DHCP)

Next week Completing IP addressing exercises Creating a logical model for your Unit 24 Task 2 Assignment Examining Classless Inter-domain Routing (CIDR)

And finally… Complete all the remaining questions from Questions to be completed for Homework if not completed. Next lesson – To construct a logical topology for Task 2 Next Week – to examine CIDR classless IP addressing