Basics of Networking - Part 2 (Connecting Internet)

For a long time network was an unknown thing, while I was using the network services without knowing how it works....

Have I understood it now? Well the answer is "partially". Yes still it is an unknown mystery for me.

But how could I write about something I don't know?
I would say. I write something that I have learned hard.... spent months and years and found a simple solution may I was in wrong direction, I had no right person behind me to teach. All you see in this blog is not learned from a course... but learned when needed, some through other sources, some through practical experience and what ever worked well after the learning is written but they are not always best.... ;-) You find a better way later or you may know it. If so please correct me when they are wrong.

Going to the topic... Let us start inter-networking (I mean, connect to internet).

What are we going to and not going to discuss in this connecting to internet

We are about to see how can we connect the entire network to internet and we are not going to discuss about single PC internet connection as that will be mostly explained by the ISP.

We assume that we are using a broadband connection to share among our network.

Always an broadband internet connection has to go through a router, also called as ADSL modems. These modems take care of two things

1. Digital signal transmission through the telephone lines.
2. Acts as a router and becomes our gateway.
   

The second point looks odd and we are not clear on what it is going to do. Let us make it clear.

Router is usually a device that is usually used to forward information between two networks, basically to connect networks of different subnet.

To access internet we need an IP address that is matching to the network of the provider (ISP). So the Router gets the IP from the ISP and on the other end it also has a local IP of our network.

Do this means it has two IPs?
Yes, it has two IPs, one end for the internet and other for our local network.
It acts as the gateway for the network. (Read - Basics of networking).
So all the internet requests navigate through this gateway and this gateway contacts the ISP to get our requests answered.

What else it can do?
This router also connects in an other mode called bridging. The bridging is a simple way of only acting as a modem and it translates the computer signals through the ISDN wire while the IP of the provider is directly assigned to the computer to which the router is connected. The bridging is possible if only one computer connects to the internet through the router.

The IP will be assigned dynamically or statically. They become active on boot or using PPPoE (Point to Point Protocol over Ethernet) dial-up.

How do we share the internet from the router?
IP Details

1. Modem/Router - 192.168.1.1
2. PC A - 192.168.1.2
3. Laptop B - 192.168.1.3
4. PC C - 192.168.1.4

All the above has same subnet and same gateway 192.168.1.1 which means the router is the gateway for all IPs.

All the PC needs DNS Server IP to identify the websites out of its network. The DNS IPs will be provided by the ISP or we can use Google's Public DNS.

Thus the ADSL router makes internet available for all the computers in the network.

While we will discuss on sharing the internet using a proxy in upcoming posts.

Basics of networking - Part 1 (Assiging IPs)

Let us start networking.... ;-) Not social networking

Since the start of the blog, we have been to the topic and this time too we are to the topic.

We are about to connect more than two computers to form a network. This involves various process to make it happen. As this blog is more about configuration management, we expect the readers to know more than basics in the computers. To start with they should know to change IP addresses in the OS.

I assume we are not about to discuss about hardware issues here and the following are correct.

1. The network cables are properly crimped and they work.

2. The network switch or hub used to connect is working good.

3. The NIC (Network Interface Card) is installed properly and is working good.

4. The OS has necessary drivers and supports TCP / IP (IPv4)

5. The user has enough rights to change and play with Network Setting in his environment

When most of us know “what is an IP Address” and “how it is useful”. We forget to understand how it really connects to more computers than what we have near us.

Hmmmmmmmmmm.................. What are we going to learn about IP Address now?

Though most of us know what an IP Address is, am adding some simple explanations to go further.

IP Address is like a name to a computer, Which we use to identify the computer, but these are not names with alphabets but with numbers. They are 4 numbers each number separated by a “.” . Each number has a range from 0 – 255 (8 bit). Eg: 192.168.1.1

To make a machine work in network it needs an IP Address to identify in the crowd and this should be unique within the network.

As we decided to connect more than two computers in a network. We are going with the following example.

The IP Address are differentiated into classes A,B, C. Since we are more into action, I would recommend to read about it more detailed. We are having a sample IP Address 192.168.1.1, Let us use this for our network. Before using we need to ensure that they are connected to each other as in the above diagram.

1. A – 192.168.1.1

2. B – 192.168.1.2

3. C – 192.168.1.3

OK. Is this IP address enough to communicate? No we need to say a subnet to make this work.

Subnet............ What is it?

Subnet is a notatation or a number used to say how many computers do this IP Address can connect and what is the starting IP of this range and ending IP of this range. The subnets are also similar to IP but they have few calculations. I would recommend to try the application in http://www.subnet-calculator.com/ where it explains the change in subnets and the change in ranges for that.

So we choose subnet 255.255.255.248 as it has range of 192.168.1.1 – 192.168.1.6 (6 computers in the network)

What happens when an IP is out of this range? How can we access it?
Here comes a gateway for the network. Which always has the door(gate) to access the other network IP. The gate way will be always the first IP in the subnet range, this is not a rule but this is a best practice to identify the gateway in any network. 192.168.1.1 is the gateway here. Setting this up in all the machines(A, B and C) should make the network accessible within the A, B and C.

So, we should be able to ping 192.168.1.2 from Machine A and C and the rest of IPs from other machines(A,B and C). This confirms the network setup.