IP and DNS Y13

IP Addressing and DNS - revision

MAC address

Task

DNS

As well as the network IP there is another important address used in networking

The MAC address is a HARDWARE address.

This is hard coded into the network card (NIC) and cannot be changed

Using DNS means that we don't have to remember IP addresses

It is constantly kept up to date

We can change the location of the web site without having to change the domain name

When we type in a URL, the address is looked up against a database of addresses on a DNS server.

If the domain is found, the address is attached to the data packet (TCP/IP)

If it isn't found, then the request is sent to another server.

They are constantly updated to check for accuracy

Complete the exam STYLE questions for this topic

It is formatted and displayed as a set of six hexadecimal numbers separated by a hyphen.

Even if the IP address changes the device can be identified by it's hardware address

If there is no DNS IP address returned then the browser will show an error message such as "Web site cannot be found'

Peer assess with purple pens

Say we have a node with an IP address of: 10.10.1.97

What is the network address?

Subnet masks

What do we need to know to find out?

DNS (Domain name system)

The TLD is furthest right, with the sub levels to the left.

Draw me a DNS tree for the following URL's:

ebay.fr

staffs.ac.uk

st-josephs.walsall.sch.uk

Yahoo.com

Class B

Address classes

• Intended for medium sized networks so many more were needed.

• The first two bits of the first octet are assigned 1 0, and the rest of the octet AS WELL AS the entire second octet is used

• This gives us 16,000 possible networks supporting 64,000 nodes each

Class C

• As we know, the IP address is split into two parts and the way it is split can vary depending upon the class

• In order to determine how it is split, a subnet mask is used.

• This mask enables us to determine the network address

• Class A addresses have the first binary bit of the first octet start with a 0, leaving 7 bits to vary.

• This restricts us to 128 possible class A networks

• It allows over 16 million nodes within the mega network

• Reserved for the largest corporations and governments

• Intended for small networks, but millions were needed.

• The first three binary digits are set to 1 1 0 and the rest of the octet AS WELL AS the second AND third octet are used.

• This leaves 256 possible nodes.

• The millions of small networks form part of the Internet - a world-wide network of networks.

IP Addressing

• The IP system has been divided into classes based on how large the network needs to be in terms of nodes within it.

• The address is split into two parts; a network address and a node address

An IPV4 address of a server isn't very easy to remember. An IPV6 would be even worse.

Domain names were developed to overcome this

Composed of a description and a suffix called the TLD (top level domain) such as .com

Combining the two gives us a unique address such as woodgreenacademy.co.uk

• The first part identifies the network itself

• The second part identifies the individual 'node' or device connected to that network.

A bit like an area code of a phone number is the same for all in a particular zone, but each connected telephone has it's own unique address.

Complete task 1 to understand more about the subnet mask

Allocating addresses

IPV6

01011110 10001000 00101000 01100111

• Each address is split into 8 bit chunks called 'octets' separated by a dot.

• The above converts to: 94.136.40.103 which is the IP address of the school website

• If you look at your home IP address it will start with 192.168.

• The 192.168 is a private IP address that will never appear on a public network

• In order to communicate on the internet this address has to be converted using NAT (Network address translation)

• This conversion is performed in your home router and turns any private address on the network into a public address

IP Addressing

Why do you think we use NAT?

• In 1981, nobody ever thought we would need 4 billion IP addresses.

• IPV6 uses 128 bits per address.

• Represented by 8 groups of four hex digits:

2001:0db8:85a3:0000:0000:8a2e:0370:7334

• Fundamental to the operation of network is the IP address.

• Every device needs a unique identity

• IPV4 uses 32 bits to represent it's address.

• IPV4 gives us about 4 billion addresses

• The allocation assigned to the USA and canada ran out two years ago.....

Lesson objectives

Dynamic VS Static

• If you run a website, the IP for your server needs to always remain the same - this is called a static IP

• A dynamic IP is temporary and is allocated at the time the device makes a connection

• One the device disconnects this IP is released for another node to use.

• A popular system for allocating IP addresses is DHCP (Dynamic host configuration protocol)

This standard gives us enough IP addresses for every grain of sand on earth!

This makes the need for NAT and DCHP redundant

• To understand the role of IP addresses in the TCP/IP network

• To understand the structure of IP addresses

• To understand what is meant by DNS and explain its function

• Most IP addresses are public, i.e anyone can communicate with them

• However there are some blocks of addresses that are reserved for private networks