Netgear EX2700 OpenWrt flash procedure

For up-to-date information, refer to the OpenWRT wiki entry (link).

The information posted below is not relevant anymore and should be ignored, as the new images can be flashed from the router's stock interface. Prebuilt images are available here. The minimal images come without a web interface, the luci images are shipped with a web interface, plus relayd and igmpproxy, for building a WiFi-extender.

First, using the web interface, update your EX2700 to the latest firmware (version 1.0.1.8 as of 2016-01-17) - older versions may work though.

For the rest of this howto, we'll assume that your computer uses 192.168.1.2, while your EX2700 uses 192.168.1.1.

The device runs a modified version of OpenWrt (KAMIKAZE, bleeding edge, r18571) by the way, but we want vanilla, obviously!

Enabling telnet

By default, telnet is disabled on this device, but there are numerous telnetenable utilities, many of which don't work with this device. I've used NetgearTelnetEnable (binaries for Linux and Windows available here).

Make sure to reset the router configuration before using telnetenable. Replace 001122AABBCC with the MAC address of your router.

$ ./telnetenable 192.168.1.1 001122AABBCC admin password
$ telnet 192.168.1.1
Trying 192.168.1.1...
Connected to 192.168.1.1.
Escape character is '^]'.
 === IMPORTANT ============================
  Use 'passwd' to set your login password
  this will disable telnet and enable SSH
 ------------------------------------------


BusyBox v1.4.2 (2015-06-05 10:24:33 CST) Built-in shell (ash)
Enter 'help' for a list of built-in commands.

  _______                     ________        __
 |       |.-----.-----.-----.|  |  |  |.----.|  |_
 |   -   ||  _  |  -__|     ||  |  |  ||   _||   _|
 |_______||   __|_____|__|__||________||__|  |____|
          |__| W I R E L E S S   F R E E D O M
 KAMIKAZE (bleeding edge, r18571) ------------------
  * 10 oz Vodka       Shake well with ice and strain
  * 10 oz Triple sec  mixture into 10 shot glasses.
  * 10 oz lime juice  Salute!
 ---------------------------------------------------
root@EX2700:/#

Permanently enable telnet in the stock firmware

root@EX2700:/# config set enable_telnet=1
root@EX2700:/# config set GUI_Region=English
root@EX2700:/# config commit

Skip stupid registration page

root@EX2700:/# config set have_registered=1
root@EX2700:/# config set http_username=<username>
root@EX2700:/# config set http_passwd=<password>
root@EX2700:/# config commit

Downloading neccessary files

The wget command does not support HTTPS, so you'll need to host the ex2700.tar.gz file somewhere else. You could either setup a simple file server on your computer, or use online services such as dropcanvas.

Be warned that wget crashes if not called with -T <timeout>.

root@EX2700:/# cd /tmp
root@EX2700:/# alias wget="wget -T 1"
root@EX2700:/tmp# wget -O firmware.bin http://downloads.openwrt.org/snapshots/trunk/ramips/mt7620/openwrt-ramips-mt7620-ex2700-squashfs-sysupgrade.bin
root@EX2700:/tmp# wget -O ex2700.tar.gz http://dropcanvas.com/<YOUR LINK ID>
root@EX2700:/tmp# tar -xzf ex2700.tar.gz
root@EX2700:/tmp# cd ex2700

Unlocking the bootloader

!! WARNING !! Modifying the bootloader environment is dangerous, and has the potential of bricking¹ your device! Proceed with extreme caution!

First, we'll make a backup of the bootloader environment partition (be careful not to overwrite /tmp/ex2700/u-boot-env.bin when using a different name for the backup file).

root@EX2700:/tmp/ex2700# dd if=/dev/mtd1 of=/tmp/u-boot-env.bak
128+0 records in
128+0 records out

Then, update the bootloader environment:

root@EX2700:/tmp/ex2700# insmod mtd-rw.ko i_want_a_brick=1
root@EX2700:/tmp/ex2700# mtd write u-boot-env.bin u-boot-env
Unlocking u-boot-env ...
Writing from u-boot-env.bin to u-boot-env ... [w]

Optional: you can use ./fw_printenv and ./fw_setenv to adjust the bootloader environment.

Flashing OpenWrt

Flashing OpenWrt is the easy part:

root@EX2700:/tmp/ex2700# cd /tmp
root@EX2700:/tmp/# mtd write firmware.bin firmware
Unlocking firmware ...
Writing from firmware.bin to firmware ... [w]

If everything is ok, we can reboot. Keep your fingers crossed!

root@EX2700:/tmp/# reboot

1: In most cases, you'll be able to unbrick your device using a serial console.

2: It is entirely possible to create an image that can be flashed via the router's stock web interface, and which passes the bootloader's integrity checks, but the kernel in that case is constrained to 982976 bytes (960 kilobytes, minus 64 bytes), because the bootloader (u-boot) expects a uImage header in the last 64 bytes of the stock "kernel" mtd partition.

SamDecrock / ex2700