8. Why Won't My Bridge Work?

I've described the intended operation of the two classes of WLAN bridging devices, i.e. the way that they should work by design. Actual implementation is usually a case of "your mileage may vary", and from what I've heard from some wireless bridge builders... it does!

Most wireless bridging problems come from mixing products from different vendors, or enabling or changing settings that aren't understood. Although the following isn't intended to be a comprehensive troubleshooting guide to wireless bridges, here are some quick things to check if you can't get your wireless bridge working:

Use the Right Stuff - Make sure that the products you buy support the modes of operation that you need. For example, wireless routers don't have bridging capability per se, but can be used with WEBs set to Infrastructure mode to build a bridge. On the other hand, AP Client mode is a vendor-specific feature, so you'd better buy two of the same thing if you're going to make this mode work.

Short Range First - Sure, you're trying to get your bridge to work across the street, or out to your workshop. But before you go for the "long shot" set up all your bridge components in the same room and try to get it working.

Pay Attention! - If you're setting up two copies of the same product, the setup screens are going to look the same. You may laugh, but I've lost track of which end of a bridge I was entering the settings on more than once! I usually write the IP address that I've set on each unit on a sticky note and always check the admin screen for the IP address of a unit before I start entering data.

Use Open System Authentication - Your product may give you the option of "Open System", "Shared Key", and "Closed System" authentication. The least restrictive is "Open System" and that's where I recommend you start. Once you get things working, you can always experiment with changing the setting to tighten up your security.

Start with WEP disabled - Similar to Point 4, you don't want to be wrestling with differences in WEP key implementation when you're trying to find out whether the bridging modes on your products are compatible. Shut WEP off until you know for sure that your products' bridging modes are compatible. Then, enable WEP.

Use Long Preamble - Some products use a mode referred to as Short Preamble. Most, however, use Long. Check for this setting and make sure you set it to Long.

Specify the (E)SSID - Don't rely on setting the SSID or ESSID of your bridge components to "ANY" to make the connection. Set them to the same ESSID, and for good security, don't use anything that identifies your location, and don't use a manufacturer's default ESSID.
Updated 15 April 2004 Using common SSIDs is not necessary when using WDS-based products and might not be necessary for bridging products even if they don't specify that they are WDS-based. See our ProblemSolver: Setting up WDS Bridging / Repeating for more info.

Enter the MAC addresses - Point-to-Point and Point-to-Multipoint AP/Bridge modes usually require that you enter the MAC address of the unit at the other end of the bridge. If you're using these modes, be sure to follow the manufacturer's instructions. Also be sure to double check that the MAC address(es) that you enter to be sure they're correct (See Point 3).