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Hooking Up a Wireless Router to DSL Service

A customer contacted us because she had moved her computer equipment and her DSL service stopped working after the move. We told her that she should plug her DSL modem into a COMPUTER (LAN) port on her router, rather than the INTERNET (WAN) port. Problem solved. "But that's not how you're supposed to connect a wireless router!" you might exclaim. We'll explain why you would want to connect your router and DSL service this way, and how to do it.

DSL connects using a technique that essentially amounts to "dial-up for high-speed connections" known as PPPoE (Point-to-Point Protocol over Ethernet), and back in "the good old days" when you got a DSL connection, you also got a DSL modem that directly connected your computer to the DSL network. The problem with that is that you still have to "dial up" to get on your DSL, one of the annoyances that cable Internet service providers conveniently remove from the user's experience.

In order to compete better with cable, the telephone companies started using a different kind of DSL modem that would perform almost all of the functions you get in a non-wireless router. Modern DSL modems typically "dial up" and maintain the DSL connection for you. One of the side effects of this is that the vast majority of these "self-dialing" DSL modems also provide router functions as well. This means that it assigns each of your computers a private IP address and is capable of "splitting" the connection such that more than one machine can use the DSL connection at once.

The big nasty problem: many of them don't have wireless capability, nor do they have more than ONE port for you to plug a computer into. They appear to work just like cable modems, where you can almost "plug-n-go" (after setting up your user name and password for the "dial-up" part), but they don't look like they have any router functions at all.

Enter your own $50 wireless router. You plug it into the DSL modem and...maybe it works, but typically it just doesn't. You also can't forward ports e.g. for gaming if you use a DSL modem with an internal router connected to yet another router doing routing yet again. What happens if you follow the directions in the router's manual is sketchy at best.

(Before you read on, you need to make sure that the DSL modem works and you can browse the Internet without issues.)

Now, enter my solution to the problem! All you need is the IP address for the router, which can easily be acquired from the ISP, or quite accurately guessed if you connect the computer to the DSL modem directly, go to a command prompt [Start, Run, "cmd"] and type in "ipconfig," and use the "gateway address" that appears there. (Type "exit" to close a command prompt.) Once you've got the IP address for the router, connect the new wireless router only to a computer. You can use the same "ipconfig" trick as above to get the router's IP address, and type that IP address into the web browser of your choice. It will likely ask for a user name and password; the most common combinations for a brand new router tend to be the following:

  • admin, (blank password)
  • (blank user name), admin
  • admin, admin
  • admin, password

Your router's instruction manual should tell you these if you're not sure. Once you're in the router's configuration controls, you can then proceed to do the following:

  1. If the router's IP address doesn't start with the same three numbers as the DSL modem, you have to change the router's LAN configuration so that the first three numbers match. For example, if the router is at 192.168.2.1 and the DSL modem uses 192.168.1.254, you need to get the router to switch over to start with "192.168.1." first. This may be called the "router IP address" or the "LAN IP address." When you change and apply this setting, you may have to re-type the IP for the router so that the first three digits match the new settings (192.168.1.1 in this example) and log back into the router.
  2. With the router's IP address and the DSL modem's IP address in the same "range," you now must ensure the DSL modem and the router don't have the exact same IP address. For example, both cannot be 192.168.1.1 at the same time as this will cause them to "break" each other when they are connected together. Change the router's IP to end in 1 or 254, depending on the DSL modem's IP. This may also be under LAN settings; however, we've seen Linksys routers where this is on the first page and you don't have to even look hard for it. If you change and apply this setting, you'll have to re-type the IP for the router as at the end of (1) above.
  3. Your DSL modem and wireless router both start with the same three nunbers (192.168.1 in this example) but end in different numbers (1 for wireless router, 254 for DSL here). The final step is to disable DHCP or "IP address assignment" on the wireless router. This prevents the wireless router from giving computers its own configuration, and allows the DSL modem with routing capabilities to do so instead. This is usually just a check box that you un-check. Once you've applied this setting, you've completed the hard part of the router configuration.
  4. You may want to take the opportunity to set up your wireless router's encryption options since you're already in there. The best bet will be WPA-PSK, as this is generally compatible with almost everything out there today and does not require any patching for most Windows XP laptops. WPA2 is stronger but somewhat incompatible, and WEP is weak but extremely compatible with practically every wireless device under the sun. All of these options keep the neighbors from, say, robbing Bank of America blind via your Internet connection (not that they're using $100's as napkins right now, given the current financial market crisis) and BofA and the FBI tracing it back to your house!
  5. Connect the DSL modem to one of the Computer or LAN ports on the back of the wireless router, not to the Internet or WAN port because it is guaranteed to fail if you do. Plug any computers into the router's remaining Computer or LAN ports, connect laptops to the new wireless network, and things should Magically Just Work(TM).

Why go through all this complicated stuff to set up the DSL connection? The alternative is setting up the DSL modem in "bridged mode," setting up the wireless router to dial-up via PPPoE, giving it your username and password, and setting it to be a keep-alive connection. Some DSL modem firmware doesn't even give you the ability to use "bridged mode" at all, meaning that you may not even have that option!

This method essentially converts your wireless router into a "wireless bridge with 3-port switch." The computers and DSL modem don't know that anything has changed, and generally speaking it hasn't. The big difference is that now you can connect your wireless devices to the same network. By cutting out a second routing system, you give yourself the ability to open ports on the DSL modem for applications such as gaming, if needed in the future, and if you replace your DSL modem with another that works the same way, you don't have to make changes to anything at all because the DSL modem being in "bridged mode" is no longer relevant. (What if your ISP took away bridging? They wouldn't, but what if they did? Your loss, eh?)

We prefer to connect all DSL clients this way. It's more easily serviced by the client if something goes wrong, and it's far faster and more reliable to set up than mucking around with PPPoE and DSL modem network bridging.

What's most important, though, is that it works and works well. Ultimately, that's all we care about.