Connecting a broadband cable modem to a D-Link DSL-2640T Wireless ADSL Router

Greetings,

I just switched from a DSL Internet broadband subscription to a cable Internet broadband subscription, and previously I used a D-Link DSL-2640T Wireless ADSL Router to allow wireless access to the DSL internet connection. Now that the internet broadband connection is through a cable modem, I wonder if it's possible to connect the cable modem to the D-Link DSL-2640T Wireless ADSL Router to allow wireless access to the cable internet connection?

Wireless router-only devices such as the Linksys WRT54G have an Ethernet WAN or "Internet" RJ-45 port which accepts the Internet (or WAN) connection from (A)DSL or cable modems though Ethernet cable. This Internet connection is then routed either wirelessly or through the router's Ethernet ports (usually 4 ports numbered 1-4).

Combo modem/router devices such as ADSL and cable modem routers, on the other hand, only have ADSL RJ-11 or coaxial cable ports, respectively, to accept Internet/WAN connections. The D-Link DSL-2640T Wireless ADSL Router only has an ADSL RJ-11 port to accept Internet/WAN connections, so there is no Internet or WAN port to connect with the cable modem's Ethernet port. The only ports that the cable modem can connect to are the 4 Ethernet ports of the DSL-2640T. I tried connecting the modem to Port 1 of the DSL-2640T, then set the DSL-2640T's WAN setup type to "Dynamic IP Address" (which is the setting for cable modem connections), but the DSL-2640T didn't pick up the cable modem's IP and DNS addresses after restarting both the cable modem and ADSL router.

I may have missed something or maybe standalone ADSL/cable modems don't work with combo ADSL/cable routers. This site indicates otherwise however:

How to set up the Linksys WAG54G as a wi-fi router only (Anders Jacobsen's blog)

I'm considering buying a wireless broadband router to go with the cable modem, but may not have to if the DSL-2640T can still be used.

Any input on this matter is most appreciated.