Firewall

[satgan]

Hi,

can anybody explain how does a firewall works and how it changes the normal mode of operation of different kinds of protocols?

Thanks in advance.

[unicman]

Main application of firewall is to separate intranet (LAN/WAN) from internet.

Firewall can be a computer or a hardware device.

Basically on internet there is a concept of IP address and port. Some of the ports are dedicated for a protocol (like port 80 for HTTP).

Now in an organization... no computer is directly connected to internet for security reasons. All network traffic happens through this device/machine called firewall. So now there is no way for any computer on internet to access a computer in organization directly. And there is no way for any computer in organization to access computer on internet directly.

Now firewall has some means of configuring it (might be web-based or a application provided by vendor). Here you can configure...
1. Which computers (identified by IPs) can access computers on internet.
2. Which ports computers in organization can access.
3. Which ports computers on internet can access.
4. Which of the computers are accessing from a computer on internet.

This way you can restrict access for computers in organization and internet.

Hope it helps.

- UnicMan
http://members.tripod.com/unicman