Problem solved:

D-Link in bridged mode connected to LinkSys WAN port.

LinkSys handles PPPoE, DHCP, etc. Operating mode is Gateway.

i have a Dlink DSL-500T as my modem/router and a Linksys WRT54GC as my wireless router.

i need help on how to configure them both to work. need big time help!!

Here's the short, simple answer:

You should set up your 500T to be a stand-alone modem and use the WRT54GC to do all the routing, NAT, etc.

First configure the 500T. Either connect it directly to a computer or to one of the LAN ports on the LinkSys. Put it in bridged mode. You will have this choice in the WAN configuration section. Save the configuration and restart the 500T.

Then connect the 500T to the WAN (uplink) port on the LinkSys. At this point the 500T will be in modem-only mode and will not have an IP address so you will not be able to see it.

Now configure the LinkSys to do the ADSL management (PPPoE or whatever your ISP has). Also set up the LinkSys to do DHCP, NAT, wireless, etc. Make sure the LinkSys is in Gateway rather than Router mode. (On my LinkSys this option is in the "Advanced" routing section.)

You may have to go to the "Status" section of the LinkSys configuration pages and explicitly tell it to connect.

Once it connects you may need to have each computer on the LAN get a new DHCP lease. You can do this from the Mac's Network setup pane.

Post again if you have specific questions.