TP-Link MR3220 v1 - Upgrade to DD-WRT and set it as Wifi Repeater

Disclaimer: Replacing the router with new firmware may render the router not usable (brick!) and loss support from manufacturer.  Do it at your own risk.

Stock ROM to DD-WRT ROM:

1. Check the hardware version:  Check the sticker at the bottom of the device.  Make sure it is hardware version v1.x.  V2 is not supported by DD-WRT yet.
2. Download DD-WRT firmware here.  Download the factory-to-ddwrt.bin.  This file will be used for first time Stock ROM-to-DD-WRT.  I use  BrainSlayer-V24-preSP2 12-22-2014-r25697 version and have not encounter any bug yet.
3. Login to TP-Link MR3220's web admin page.  The web page is usually 192.168.1.1.  The default username and password is admin / admin.
4. Go to System Tools - Firmware Upgrade.  Browse the "factory-to-ddwrt.bin".  Click "Upgrade" to start upgrade.
5. After a while (about one to two minutes), the router should finish upload and upgrade, and the web page will be reloaded.  You will be prompted to enter username and password for DD-WRT.

Config it as Wireless Repeater
(Reference: http://www.dd-wrt.com/wiki/index.php/Client_Bridged)

1. Assume that your network environment is as below:
1. Wifi Router is 192.168.1.1 which route all your LAN traffic to/from Internet.  SSID is mySSID.
2. Your MR3220 (repeater) will need to use another IP, say 192.168.1.250. 
2. You may need a network cable to connect to your DDWRT router.  You need to assign a fix IP to your network card since DHCP server will be disabled very soon.
3. Go to Setup - Basic Setup.  Setup the below:
1. WAN Connection: Disabled
   IP change: 192.168.1.250
   Subnet Mask: 255.255.255.0
   Default GW: 192.168.1.1
   Local DNS: 192.168.1.1
   Disable DHCP
   Enable Assign WAN port to Switch
2. Remember to click Save.
    
4. Go to Wireless - Basic Settings.  Setup the below:
1. Wireless Mode: Client Bridge (Routed)
   (Note: MR3220 does not offer a repeater mode.)
   Channel Width: Full 20Mhz (Note: Do not set Dynamic, I encounter instability with Dynamic)
   Wireless Channel: Auto
   SSID: mySSID
   Network Configuration: Bridged
2. Under "Virtual Interface", click "Add."
   Wireless Mode = "AP"
   SSID = mySSID
3. Click "Save"
5. Go to Wireless - Wireless Security
   
   1. Setup the Wireless Security for both Wifi Interface.
6.  Go to Security - Firewall
   
   1. Disable SPI Firewall
7.  Go to Setup - Advanced Routing
   
   1. Change operation mode from Gateway to Router (so that not NAT will be performed)
8.  After all setup done, click "Apply Settings".
9. You should set your computer back to DHCP and perform checking.