The Problem
The beetel DSL modem installed by Airtel has the IP address set to 192.168.1.1. The Linksys router (and probably other routers as well) use the same IP address (192.168.1.1) as their default IP address for accessing their configuration page. This causes an IP address conflict and hence the router wouldn’t be able to forward IP packets to the modem.

The Solution
1) Insert the installation CD/DVD provided with the wifi router and follow the instruction for installing the router. During the installation (Probably at the final step) the router will fail to detect Internet connectivity. That’s fine, as this is the problem we are resolving. Leave the setup window open and proceed to next step.
2) Open your favourite web-browser and enter the following address in the URL bar : 192.168.1.1
3) The above step should open the Linksys configuration page. If you are prompted for a username and password, enter admin for both the fields. If you had set a router password in step 1 enter username as admin and the password you had set in step 1. Before the username and password is asked you might be displayed a page with 3~4 icons, labeled WAN, LAN etc. select the WAN Icon, enter the username and password as described above, if prompted for.
4) On the page displayed select Setup tab (most likely the first tab) and under that select Basic setup (The exact name/text might vary but would most probably be something similar). Scroll down and locate the field Local IP address. The default value for this field would be 192.168.1.1, change it to 192.168.0.1.
5) Scroll further down the page and click on Save Settings. Reset your router and DSL modem (Power them OFF, wait for 10~15 seconds and power back ON). Wait for around 1~2 minutes (So that the Router and DSL modem have properly rebooted).
6) Complete Installation of the router (Click ‘Try Again/Re-try’ in the setup window we left open in step 1)

You should now be able to browser Internet properly on the wired (directly connected) computer. Setup your Laptop and Desktops with WiFi Ethernet card/adaptors to connect to the WiFi router. After that you should be able to access Internet through them.

Tips

• Always setup a WPA/WEP key (pass-phrase) for your WiFi router for thwarting unauthorized WiFi piggybacking.
• For most users WPA Personal (with default settings) should work good enough. You can set/change the pass-key for WPA Personal by logging to the web-based router configuration pages. Select Wireless tab in the configuration page and under that select Wireless security. Select WPA Personal for security Mode field and Change the field labeled WPA Shared Key. This is the key you will enter when connecting to your WiFi router form you laptop or other computers with Wireless Ethernet cards.
• Do not buy the WiFi router provided by Airtel , it is expensive (around Rs.500~Rs.1000 more than other similar quality routers) and from their own company Beetel (Yup, Beetel is owned by Bharati group). And I haven’t heard/read good reviews about Beetel WiFi routers.
• Remember: to access the Router configuration pages you need to enter the IP address you entered in step 4 (192.168.0.1), the address 192.168.1.1 will take you to DSL modem’s configuration page.
• Default username and password for DSL modem is admin and password respectively.
• You may remove the directly connected computer after your WiFi router is setup properly. You need a directly connected computer for fist time installation and configuration of the WiFi router.

I hope this post was of some help to all the Bharti-Airtel broadband users. Thanks for reading.