i have a CentOS server that has two NIC cards; eth0(217.21.119.17) connects to the internet whereas eth1(192.168.0.1) connects to a LAN. some kindly direct me how i can make the computers on the LAN access the internet(NOTE: The server has access to both networks). Please explain elaborately since i am doing this for the first time.

It is probably beyond the scope of a forum like this to explain what you need in extreme detail, however there are a few online resources that do this, as well as some products that will both simplify and improve the quality of your product. One article I find quite well done is http://librenix.com/?inode=9837. You can use a GUI tool or canned package to create a good firewall/router. Two examples of these are homeLANSecurity and Firestarter. These offer the advantage of someone else's expertise being built into your final product, as well as significantly reducing the learning effort.

Do you have the two ethernet interfaces working now? If yes, you are already well on your way. Have a go at it, and come back here when you bump into a problem. For further research, try Googling "linux router firewall".
--- rod.

You need to setup a basic iptables firewall and install ip-masquerading; see this guide.

Once you have this established then configure the IP addresses on the lan to the same subnet. It is often easier to use static addresses but you can also use dhcp. You must assign IP addresses in the range 192.168.0.2 - 192.168.0.254. When you have done that then set the gateway for each box on the lan as 192.168.0.1. You should be good to go.