Unbrick a Netgear WNR3500L V2

It finally happened… After experimenting with alternative firmware for my WNR3500L router, I uploaded the wrong version and converted the device into a rather expensive paperweight. After some searching, I found this page, explaining how to revitalize the router by using a USB-TTL converter cable. You can get  (e.g. CP2102 Module Modul USB to TTL Converter) for a few bucks Ebay, but expect a few weeks for the delivery from China.  If you follow the tutorial on the OpenRouters page closely, it should work out quite nicely.

Update: 2018-01-21

It happened again. I flashed an unsupported version of LEDE on the device and it did not want to boot again. I followed the same procedure as described here, but the router was complaining about a version missmatch of the device ID and the image ID. Turns out, I had to explicitly use binary mode for FTP. Here are the steps again.

  1. Connect the serial cables as shown
  2. Make sure router is off
  3. Launch minicom in a terminal and make sure the settings are valid for ttyUSB0
  4. Boot the router and immediately press Ctrl+C in the terminal
  5. Type tftpd in the prompt, the router should start a FTP server on 192.168.1.1
  6. Open a second terminal, cd into the directory where the firmware is
  7. Make sure its the right version 🙂
  8. Start the FTP client: ftp 192.168.1.1
  9. Change to binary mode (this is very important): mode binary
  10. Move the file: put FIRMWARE.chr
  11. The router should detect the file and process it
  12. Reboot and enjoy

Connecting a Serial TTYUSB Device to the Router

 

USB-TTL

When you see this message below, you need to abort the boot process.

Willkommen zu minicom 2.7

Optionen: I18n 
Übersetzt am Feb  7 2016, 13:37:27.
Port /dev/ttyUSB0, 17:47:29

Drücken Sie CTRL-A  Z für Hilfe zu speziellen Tasten
Found a Samsung NAND flash with 2048B pages or 128KB blocks; total size 128MB
Decompressing...done


CFE for WNR3500Lv2 version: v1.0.9
Build Date: Fri May  6 11:54:17 CST 2011 
Init Arena
Init Devs.
Boot partition size = 262144(0x40000)
NFLASH Boot partition size = 524288(0x80000)
et0: Broadcom BCM47XX 10/100/1000 Mbps Ethernet Controller 5.60.136 
CPU type 0x19749: 480MHz
Tot mem: 131072 KBytes

Device eth0:  hwaddr 84-1B-5E-4E-FF-84, ipaddr 192.168.1.1, mask 255.255.255.0
        gateway not set, nameserver not set
Checking crc...done.
Loader:raw Filesys:raw Dev:flash0.os File: Options:(null)
Loading: .. 3848 bytes read
Entry at 0x80001000
Closing network.
Starting program at 0x80001000

When pressing Ctrl+C does not work, make sure your minicom settings look like this:

A - Serieller Anschluss      : /dev/ttyUSB0                           |
B - Pfad zur Lockdatei       : /var/lock                              |
C - Programm zur Rufannahme  :                                        |
D - Programm zum Wählen      :                                        |
E - Bps/Par/Bits             : 115200 8N1                             |
F - Hardware Flow Control    : Nein                                   |
G - Software Flow Control    : Nein

 

2 thoughts on “Unbrick a Netgear WNR3500L V2

  1. Just for curiosity:
    I have bricked up my Netgear. but I can not start TFTPD on my router. It looks like Netgear does not enable any ethernet port:

    CFE for WNR3500Lv2 version: v1.0.9
    Build Date: Fri May 6 11:54:17 CST 2011
    Init Arena
    Init Devs.
    Boot partition size = 262144(0x40000)
    NFLASH Boot partition size = 524288(0x80000)
    CPU type 0x19749: 480MHz
    Tot mem: 131072 KBytes //My remark – after this line, there should ethernet info appear, but there is nothing

    Committing NVRAM…done

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