From DD-WRT Wiki
This page applies to version 2. For version 1, see Linksys E1200
 Hardware Information
|CPU Speed||300 MHz|
|Flash ROM||8 MB|
|WLAN Max Speed||300 mbps|
|Switch||4x 10/100 LAN + 1 10/100 WAN|
 Flashing Instructions
After using the e1200v2 build file for the initial flash from stock, only use broadcom K3X-nv64k builds to upgrade with or you will brick your unit. Use builds past 18946.
Don't confuse this unit with some of the other Linksys E-Series units that use nv60k builds, this one uses nv64k builds!
- These intructions were done with an e1200v2 running FW_E1200_v2.0.07.002_US_20150108.bin
- Grab ftp://ftp.dd-wrt.com/betas/2012/07-20-12-r19519/broadcom_K26/dd-wrt.v24-19519_NEWD-2_K2.6_mini-e1200v2.bin and ftp://ftp.dd-wrt.com/betas/2016/04-25-2016-r29519/broadcom_K3X/dd-wrt.v24-29519_NEWD-2_K3.x_mega-nv64k.bin (or later)
- Log into the stock firmware webadmin http://192.168.1.1, via an ethernet port (preferred). You can flash over wireless but it's not recommended, you could more easily end up with a bad flash and brick your router.
- Do a reset using the stock web interface. Wait a minute.
- Flash the firmware dd-wrt.v24-19519_NEWD-2_K2.6_mini-e1200v2.bin
- Wait 2 minutes. It will reboot on it's own.
- Wait about another 2 minutes until it finishes booting.
- Log into the dd-wrt web interface at http://192.168.1.1
- Flash dd-wrt.v24-29519_NEWD-2_K3.x_mega-nv64k.bin
- You are done.
Current Editor's Note: 2016-05-08 These instructions were corrected for general readability. Process was tested on two e1200v2 units.
 Build Information
Current Editors note: (2016-05-08) I did extensive flashing with this router, to update these instructions. I have removed grammar errors, and other confusing non-relevant text. I spent many hours getting this figured out.
Following the initial flash instructions from stock to dd-wrt with ftp://ftp.dd-wrt.com/betas/2012/07-20-12-r19519/broadcom_K26/dd-wrt.v24-19519_NEWD-2_K2.6_mini-e1200v2.bin, use builds with K3.x and nv64k in the name for upgrading, like ftp://ftp.dd-wrt.com/betas/2016/04-25-2016-r29519/broadcom_K3X/dd-wrt.v24-29519_NEWD-2_K3.x_mega-nv64k.bin. Any other builds for upgrading an existing dd-wrt install without K3X and nv64k in the name will brick your router! Build must be greater than 18946. For the safest results, use builds that are linked within this wiki as they have most likely been forum tested with ok reported results.
This router uses k3x builds and not k26 or k24 builds, although supposedly (and this does work, tested 2016-05-08) you must initial flash from stock to dd-wrt with a k26 e1200v2 build, for example this: ftp://ftp.dd-wrt.com/betas/2012/07-20-12-r19519/broadcom_K26/dd-wrt.v24-19519_NEWD-2_K2.6_mini-e1200v2.bin. To find the latest builds, you can browse the DD-WRT file server and look for the broadcom_K3X folder, in there is the appropriate for your unit.
If the file is larger than around 7.9MB for this router, the build will not work.
 More Information
If you use the old Wiki instructions (not here anymore), it will screw up your flash and you will end up with non working Ethernet ports, only WiFi. Reference http://www.dd-wrt.com/phpBB2/viewtopic.php?t=277707
Old Forum thread: http://www.dd-wrt.com/phpBB2/viewtopic.php?t=153176
 Reverting to Stock Firmware
Download the stock firmware image from the manufacturer's website (link), reset the router back to defaults using a 30-30-30 hard reset, then flash the stock image from within the dd-wrt webgui. After 5 minutes it should finish, you will then need to do another 30-30-30 reset and then access the stock webgui @ 192.168.1.1