For SMC7904WBRA :: How to use Cable Modem on ADSL router/modem

YES THATS TRUE. TO CONFIGURE THE ROUTER. NEED THE PPPOE USERNAME AND PASSWORD FROM THE INTERNET SERVICE PROVIDER. VPI AND VCI SETTINGS.
..THEN ACCESS THE ROUTER PAGE
..GO TO ADVANCE SETUP PAGE.
..THEN LAYER2 INTERFACE
..CLICK ADD
..CONFIGURE THE SETTINGS.
..POWER CYCLE THE NETWORK.

Check to see if you can plug the wan port to your adsl modem and then plug your pc to the router. on ADSL, some ISPs will record your mac address to avoid sharing. Just see I your router supports cloning your mac. All you do is login to your router from your pc, and it should be under your Wan settings. Use DHCP unless specified otherwise, and ensure to enter any pptp login info if your ISP provided any.

Contact your ISP. Some ISPs limit the number of computers that can simultaneously connect to your cable-modem. If you change computers, you have to tell your ISP.

Or, power-off your cable-modem, to "reset" it.
Connect the Cisco Router to the cable-modem.
Power-on your cable-modem.
Power-on your router.
Connect your computer to your router, and see if you get Internet access.

try to reset modem/router and then configure again.

I'm guessing DSL to CABLE switch? Most will tell you no but it can be done. ISPs commonly use dual modem/router type devices in order to charge some sort of fee every month to the consumer.

Essentially what you're going to be doing is running a line from your wall to the modem. Now instead of running a line directly from the modem to the PC what you're going to be doing is I believe plugging it in to the 4th position on the back of the combo device. 1st you may have to reconfigure the device for your new ISPs information ie. DNS SUFFIX, IP ADDRESS, etc. Don't quote me on this but I believe to do that you'll have to connect the ethernet line directly from the PC to the combo device via port 1 on the device. That will enable you to configure the device as you would any other router. 

It's all a bit of a pain in the rear but it can be done. I've noticed forums around the net describing the process in further detail but without model specific information the best I can say is yes someone somewhere would know how to do it so don't let anyone especially your ISP say that it can't be done.

Best of luck! 

Sean

Source: Personal experience switching from VZW to COMCAST =]

no you cannot have 2 modem/routers, only another router

what is used this router it is a adsl router or only router if this is only router then you have to connect your adsl modem then only its work properly .

Unplug the plug (from phoneline) on back of USB modem, plug into Zoom router. Plug one end of an ethernet cable into router and one end into your PC. Type http://10.0.0.2 into a web browser (eg. Firefox or Internet explorer) username/password is admin/zoomadsl go to basic setup and input your ISP username and password (the one given to you by your internet provider) under PPP. Click configure my connection. Save changes and then write to flash (both buttons on bottom of page)

In general the Wan port of the router gets connected to the ADSL modem where the computer used to connect and the computer connects to the switch portion of the router which often has 4 ports. The router has configuration options that must be set to comply with your internet service providers (ISPs) requirements. These can often be found on his support web site. If you can provide the link to the website I can assist with the search. Otherwise I will need the name of the ISP. If this ISP is cable related like Road Runner I will need the associated cable provider. I will also may need to know the country, city and state in which you are located as some ISPs have geographic differences in equipment. Depending on what that information determines I may also need to know the Manufacturer and Model of the DSL Modem -- probably the box your computer plugs into when it is working. It would also be helpful to know if you got the router used or new. Used routers may have been configured by their previous owner and require additional changes to new routers with factory default settings.

Lastly as a wild guess. There are some ISPs that extract address information (MAC Address) from the attached network card into the units they send you to attach to the phone line or cable. Should you happen to be with such a company they often state turn on the modem before the router so it recognizes the change. You may want to try turning off the modem attaching the router without power then turning on the modem wait a minute and power on the router -- if your ISP requires default settings for your router and it was new this may work. As far as the alarm for unplugged cables -- do the cables have the clip portion on the ends and are they securely established in the ports. Are the contact points on the cables free of dust and dirt? Especially if the router is used have you tried a different port for the computer side connection? In case of the computer end have you tried multiple computers -- possibly a friend's if you do not have more than one.

There is a strong likelyhood this simple solution will not work. All of the above information may lead to the determination that we must enter a static IP address into the router, maybe we need to provide for PPPoE login for the router, maybe we need to configure the switch to allow the router to perform the PPPoE login, and several other such items. This is probably not a one reply solution.

Did you have DSL prior? if so, was the MAC address cloned to the router? You may need to check that setting, its pretty common with this type of setup