How to: Build a Wireless Bridge Using DD-WRT, Part II

By Aaron Weiss

September 30, 2009

As a complement to our popular tutorial series on DD-WRT, this new series offers a helpful overview of wireless bridges and repeaters, as well as pointers and step-by-step instructions.

In 2006, we published an introductory tutorial on setting up a wireless bridge using DD-WRT. While most of that tutorial is still relevant today and thousands of readers still flock to it every month, our readers often express an interest in learning more about DD-WRT and how to create wireless bridges and repeaters with it. In response, we’ve put together this new tutorial series. In the first part, we offered a helpful overview of wireless bridges and repeaters. In this second installment, we get down to the nitty gritty.

DD-WRT recipes

Configuring any of the four modes in DD-WRT requires a similar recipe, each with just a few small differences.

In all cases, your primary router does not need to have DD-WRT installed. In fact, it can be any wireless router. You do not need to change any settings on your primary router, although you should know how to log into it to read some settings.

For your secondary router, refer to our previous stories about finding a DD-WRT compatible router and flashing the DD-WRT firmware.

Once logged into your DD-WRT router, let’s begin by looking at the first configuration screen, Setup/Basic Setup.

setup_basicsetup_sm.jpg

Click to enlarge.

When configuring your router for either wireless bridge or repeater bridge modes, both items in the figure above marked 1 and 2 will be disabled. You can manually disable them here, but DD-WRT will automatically disable them when you select one of these modes in the next configuration screen.

It is important to choose a sensible “Local IP Address” for item 2:

  •  In either bridge mode, choose an IP address that is compatible with the IP address scheme of your primary router. For example, if your primary router is 192.168.1.1, then you could enter here 192.168.1.2.
  • In either non-bridged mode (wireless client or wireless repeater) you should choose an IP address that is different from your primary router. For example, if your primary router is 192.168.1.1, then you could enter here 10.0.0.1 (see here for more on private IP address ranges).

Once finished, be sure to click the “Apply Settings” button at the bottom of the page. If you’ve changed the IP address, the router will automatically reboot and your connected machine will need to receive the new address. If you are configuring a bridged mode, which means DHCP is now disabled on the router, the router will not automatically assign a new address to your machine. When the router reboots, you will need to temporarily assign a manual IP address to your machine (details for Windows or Mac) to re-connect to the router and continue with configuration.

We next move onto the Wireless/Basic Settings page:

wireless_basicsettings_sm.jpg

Click to enlarge.

From the Wireless Mode menu (marked 1 in the above figure) you will choose either Client, Client Bridge, Repeater, or Repeater Bridge.

Set the SSID (item 2) to the network name broadcast by your primary router. If you don’t know its name we can actually scan for this information later and DD-WRT can fill in this field for you.

Now click “Apply Settings.” If you’ve selected either Client Bridge or Repeater Bridge modes, DD-WRT will now automatically disable the “Connection Type” and “DHCP Server” settings on the first configuration page.

If you are configuring either a repeater or repeater bridge then you need to create a virtual interface. This will be used to re-broadcast a wireless signal. To do this, click “Add”:

wireless_addinterface.jpg

A new virtual SSID will be created, for which you need only complete the name (item 1 in the above figure). This will be the network name that is broadcast by this router—it should be different from the network name broadcast by your primary router (i.e. different from the network name in the previous figure).

Again click “Apply Settings.”

Next we move to Wireless/Wireless Security.

wireless_security_sm.jpg

Click to enlarge.

First you must configure the security settings for “Physical Interface.” This refers to the signal you are receiving from the primary router. Regardless of which client or repeater mode you are configuring, these settings must exactly match the security settings of the primary router! If they don’t, then this router will not be authorized to connect to the primary router.

Of course, this assumes that the primary router has wireless security enabled—if not, you can set “Security Mode” to “Disabled.”

If you selected Repeater or Repeater Bridge on the previous screen, you will also see the “Virtual Interface” security settings, as pictured in the above figure. Here you specify the security settings of the re-broadcast signal operating under the virtual SSID you configured earlier.

You can set “Security Mode” to “Disabled” to disable security on the re-broadcast signal (this does not effect security on the original signal from the primary router!), or you can configure another type of security for the re-broadcast signal. This is completely independent from the security on the primary router—you can even set a different password (or “shared key”).

Click “Apply Settings.”

Almost there—if you are configuring either client bridge or repeater bridge mode, then you want to disable the firewall in DD-WRT. This is because you will be part of the primary router LAN, and that router is providing firewall functions. Simply click to Security/Firewall and disable the “SPI Firewall” option (and “Apply Settings”).

Now, to see if all configuration items are set correctly and the secondary router can actually receive a signal from your primary router, we can look at the Status/Wireless page.

status_wireless_sm.jpg

Click to enlarge.

Here we see whether the secondary router is actually talking to your primary router. You should see an entry listed in “Access Point & Clients” as marked with an arrow in the figure above. Here you see the signal strength of the connection to the primary router.

Note that this signal strength can be quite low and you may still enjoy a stable connection.

If you have configured for either client or repeater modes (non-bridged), then your router should have obtained a WAN IP from the primary router. You will see this listed in the summary at the upper right of the page, marked with a red arrow in the above figure. If you do not see an IP listed here and you are in one of these modes, that means you have not successfully associated with the primary router—which could be the result of poor signal strength or an incorrect setting, such as security parameters.

(If you are using bridge mode, you will not see a WAN IP listed, which is normal.)

You can click the “Site Survey” button at the bottom of the page to launch a scan of available wireless networks. You can join a network this way, which DD-WRT will remember in place of the SSID setting you manually typed into the page at Wireless/Basic Settings.

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