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.