I discovered an old thread when I was trying to figure out a solution for getting a cheap wireless bridge for a store's Point of sale (POS) system. I spend perhaps a few hours figuring things out and finally got it to work.
DIR505 Can work as a wireless bridge to connect to your main router wirelessly (bridges) and shares that connection with the built-in ethernet port.
The POS needs to actually access the Internet to work, but would only take an wired connection. I got it to work, and also tested this on a PC too. The speed within the indoor distance is very nice, almost at the full bandwidth of my connection.
Here is what I did. I set the DIR505 as a Repeater, then hid its SSID since I don't really want it to repeat. Then I set the LAN IP to within the subnet of the main wifi router the 505 is connecting to (as a client) without conflicting with main router DHCP server settings.
i.e. My main router is in 192.168.1.xxx, so I set make sure the main router only assigns IP from 192.168.1.10--- 192.168.1.250. DIR505 would have a static IP of 192.168.1.251 and submask of 255.255.255.0 and gateway of 192.168.1.1 (if needed)
Then I disabled the DHCP server function on the DIR505, since I don't want it to touch IP assignment at all. Then I need to set my POS to a static setting that'll work with the main router.
IP: 192.168.1.253
Mask: 255.255.255.0
Gateway: 192.168.1.1 (Main router IP)
Up to this point, this would've worked for any device within the LAN (ie. Network printer), but since my POS needs internet access, so I need DNS as well to resolve the name address. My DHCP is disabled on DIR505 and the main router isn't assigning anything to the POS with 505 in-between, so I had to manually set the DNS setting.
Prim DNS: 8.8.8.8
Sec DNS: 8.8.4.4
(Those are Google DNS IP's)
After that, reboot first the 505, then the POS (or PC), it will work right after the reboot. The wiring is as simple as: DIR505 --- POS. The main router is sittings somewhere in the other room.
Hope this helps for anyone who's still using DIR505. It's more useful than we had expected!