Using ADSL router for cable internet

Hello Experts!!
I have a KabelBW connection (cable internet in Germany) and I would like to go wireless with linksys WAG160n (router + gateway) which I assume could work like a router.

So the situation is:
Laptop -> cable modem -> internet
this works!

Situation I want it:
Laptop -> ADSL router -> Cable modem -> internet
This doesn't work

When I connect this combination via ethernet cables, it works (as router starts working as switch) but when I use wireless, the connection between router and modem doesn't work.
I have cloned MAC address and have disabled DHCP of the router to avoid any conflicts with the modem.
Any help would be greatly appreciated.
Thanks,
anomad