I have two identical TP-Link TL-WR1043ND routers and they are both flashed with DD-WRT (build 20548). I connect these two routers together with a wired router and the tutorial is here. The new setup is wired router to wireless router and then wireless router. The two wireless routers are act as WDS (Wireless Distribution System). The firmware of DD-WRT can be download here.
At the tab of "WDS" on each router, make sure they are set to "LAN" and set to other's MAC address. Select "Lazy WDS" for both routers and "Apply Settings".
Make sure all the wireless setting on the both routers are identical, such as channel and etc. Also make sure the security wireless setting are disabled on both routers at the moment. We will enable it later.
The wireless router that is connected to the wired router is A and the other wireless is named B. Make sure to disable the firewall at the router B which is not the one connected to the wired router.
On the router B (which is not connected to the wired router), set the Internet "Connection Type" to "Disabled". The "DHCP Type" is set to ""DHCP Forwarder". The "Local IP Address" is set to the same network (subnet) of the wired router but in a different IP address. The "Gateway" is set to the address of the router A that connected to the wired router. The "DHCP Server" is set to the address of wired router.
For example, wired router IP address is 192.168.0.1 and it is act as DHCP server. Router A address is 192.168.0.80 and the settings is same as the captioned link at the beginning of this article. Router B address is 192.168.0.90 and the gateway is set to 192.168.0.80 and the DHCP server address is set to 192.168.0.1.
Enable the wireless security setting on router B and then A. They should be identical too. Now, you can connect to the internet properly without problem.
That's all! See you.