Categorized | Hacks & Mods, Hardware

Setting up DD-WRT as a Wireless Bridge or Repeater

Posted on 27 August 2010

DD-WRT Wireless Bridge DifficultiesDD-WRT is a popular alternative firmware that runs on select wireless routers that extends the functionality of your typical home router to that of a commercial network appliance. It enables you to change your router into an access point, wireless bridge, wireless repeater or even a wireless adapter. If you’re not running DD-WRT , it’s like your router went to community college to learn how to route internet traffic whereas your neighbors DD-WRT router graduated Summa Cum Laude at M.I.T.

This article aims to help troubleshoot problems you may encounter when trying to set up a wireless bridge between two different models of routers. It isn’t a replacement for the tutorial on how to set up a wireless bridge , which may differ from build-to-build. Here’s where you’re most likely to get snagged, and what to do.

THE WHY

You’ve followed the instructions on how to set up a wireless bridge exactly. The problem is when you’re using two different routers, they may deal with speed, encryption, and channel differently. Both routers don’t have to be running DD-WRT, but they do have to have the same settings and things aren’t always as they appear…

The problem is, even if you’re running DD-WRT on both routers, if they don’t have the same chipset using an identical configuration through the routers GUI may not configure two different routers to operate exactly the same. For example, when using a 802.11G router to repeat the signal of a 802.11N router you have to limit the fastest router to the slowest router in your setup. If both of your routers are running on the same chipset (usually Broadcom, maybe Ralink) you’ll probably have a better time unless they’re of different generations.

My friend lives in the attic of a large three story colonial home in Pennsyltucky. Her landlords have a newer highend NETGEAR router running stock firmware on the 2nd floor. The reception was horrible, and she hadn’t been selling enough handmade jewelry on her website to get her own damn internet (shameless plug) so I decided to set up a wireless bridge. I used two routers: Buffalo WHR-300GN (Ralink) and a Linksys WRT54G (Broadcom), one on each end of her floor. So, if your DD-WRT won’t work as a wireless bridge, read on to find out how I made them all jive (finally!)

THE FIX

  1. Check to see if the speed settings you have selected on each router are truly identical.
    Each router implements backwards compatibility for lower speeds and “fall back” for clients with poor signal strength differently, so you may need to explicitly pick an N, G, or B-only setting rather than a combination/compatibility option such as 802.11/B/G/N.When you’re dealing with two different routers you can’t expect any combination mode or backwards compatibility mode to function identically, pick a speed/band/frequency and stick with it!
  2. Insure both routers are set to the same channel.
    Is either router set to Auto? If so, follow standard procedure for setting up  a wireless network and check for vacant channels using DD-WRT‘s built-in site survey tool* or manually check what neighboring networks are using and decide on a channel. Make sure both routers are explicitly set to this channel.
    *The site survey doesn’t work on all models even if it is present, so don’t get frustrated or waste too much time here.
  3. Decide (or reconsider) what type of encryption you will be using to insure each router is truly identically configured.
    In any case you want to use the strongest encryption you can use, however, when setting up a wireless bridge you’re going to have to settle on an encryption setup that both routers explicitly support in similar manners.

    You have to deal with this the same as the speed and often you’ll run into trouble with backwards compatibility modes. Perhaps one router says TKIP/AES and the other says AES/TKIP. You need both routers to be set exactly the same, their preferred encryption scheme and fall back must be identical. Until you get the wireless bridge to work, just as with the speed and the channel it’s best to explicitly set the encryption to whatever both routers support, you can always go back and change it later.
     
  4. Try rebooting the routers when tweaking any of these settings; even if it’s not required.
    This may be the difference between finding the magic combination of settings both routers must have. You may end up setting up the routers the way they need to be for your configuration, but somehow the settings weren’t applied and you end up skipping over them, never to try that combination again because “you already tried it.” This is a good time to make sure you are fully aware that the Save and Apply buttons do different things!
     
  5. Use your intuition and Google
    Is there something we’re missing here? Think about what settings might be causing the routers to fail to properly route traffic even when the wireless bridge is configured correctly. It doesn’t matter if you followed the instructions to a T, if a single setting that influences how the routers interact with each other is wrong, it’s enough to make a wireless bridge to nowhere. A wireless bridge is like two routers dancing, they have to be moving to the same rhythm if they’re ever going to get down and dirty and show each other their LAN side.
     
  6. Let us know what works!
    If the setting you had to change wasn’t mentioned here, please help anyone struggling to set up a wireless bridge by commenting with what you had to do (be sure to include what models of routers and what firmware they are running) to get your bridge working so you could watch cat videos on YouTube right after you’re done donating to this website for ending your hours of frustration (shameless plug #2).

1 Comments For This Post

  1. kev says:

    good write up

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