When you try connecting the linksys wireless router (wrt54g with ptcl broadband in my case) it doesn’t get configured automatically and the internet don’t work.
To fix the issue of internet not working on linksys wireless router or any other router after connecting it to a different adsl model you simply need to release and renew the DHCP.
Click here : If you can’t access linksys wrt54g admin panel
For linksys wrt54g do this to release and renew DHCP:
Login to linksys wireless router admin control panel (usually by 192.168.1.1) in web browser and login
Goto: Status (first sub page will open itself: Router)
At the bottom of the page find 2 buttons: DHCP release and DHCP renew
Click them one by one and wait for a while.
Disconnect the wireless internet from your device and connect again in case renewing don’t fix the problem.