From DD-WRT Wiki
A router running DD-WRT v24 is able to create a wireless bridge. The bridging mode is selected from a drop down menu on the Wireless > Basic Settings page.
There are several variations on bridging. Use the following to determine which type is best for you. See the linked tutorials for information and examples of different bridge types.
 Client Mode
(aka: Client Mode Wireless) In this type of bridge, your DD-WRT router connects (using radio) to an AP (access point) or wireless router. The DD-WRT router creates a subnet LAN. The subnet LAN has clients connected to it with cable connections. (On the firmware page, the menu choice for this mode simply reads “Client”.)
 Client Bridge
The previous page remains for reference Wireless_Bridge
 Broadcom WiFi
In this bridge, your DD-WRT router connects to an AP or wireless router and extends the original LAN. No subnet is created. Wired clients connect to your secondary router. Both routers are in the same LAN.
- If you don't require extending the range of your wireless LAN, this is probably your best option. An example of this is hooking up one or two wired computers in a bedroom where there is no wired connection. The DD-WRT router is located in the bedroom and the computers plug into the router.
- An advantage of a client bridge is having secondary computers obtain their DHCP leases from your main router. Furthermore, you don't need to set up port forwarding on your secondary router. Security measures and access limits are controlled by your main router.
 Atheros WiFi
This MAY not work reliably with atheros wifi. Many problems occur, so you should stay away from it. Better use Atheros WDS#Atheros
 Ralink WiFi
 Repeater Bridge
This bridge is like a client bridge, except it adds the functionality of extending the range of your wireless network. The range is extended because, presumably, your secondary router is some distance removed from the main router. In repeater bridge mode, a wireless client can connect to either your main router or your secondary router (repeater bridge).
- Unless you need to extend your wireless coverage, it's not preferable to employ repeater bridge mode. Some of your radio bandwidth will be consumed by the repeater function.
Other modes not discussed here are AP, Adhoc and Repeater. Although these modes employ the router's radio, they are not considered to be bridges.