Unbricking My TRENDnet TEW-812DRU Wireless Router

Upgrading my TRENDnet TEW-812DRU v2 router with DD-WRT firmware sometimes goes smoothly, and sometimes not. Usually if the upgrade fails on the first try, I can just unplug the router, wait 10 seconds, plug it in again, wait for the web UI to come up again, re-upload the firmware (and wait), and the upgrade will work on the second try.

But sometimes the router won't boot up correctly. All the blinking lights come on as normal, but it doesn't do any actual routing — or provide any DHCP services, which makes the router look bricked, even for devices connected to it physically with an ethernet cord.

But fortunately, it's not actually bricked. The router still grabs its usual local address (192.168.1.1, if you haven't configured it to be something else), and runs its nifty "TRENDnet - Emergency miniWeb Server" on port 80. The emergency page served up allows you to upload a new firmware image — and every time (so far) that I've gotten to that page, I've simply been able to upload the firmware image I've been trying to install (ie the latest trendnet-812dru-webflash.bin file from DD-WRT); and the router accepts it, installs it, and reboots itself, and everything is back to normal and happy in a few minutes.

The trick to accessing the router when its usual networking services are down is to 1) connect a computer to the router via wired ethernet connection (if you don't have one set up that way already), and 2) configure that computer with a static IP on the router's local subnet.

Since I'm running my router at 192.168.1.1, I just set the computer's static IP address to 192.168.1.10, and point its browser to http://192.168.1.1. The emergency web server seems to listen only for a minute or two after booting, though, and then goes way; so if the emergency page won't load, I unplug the router, wait 10 seconds, and plug it in again.

And since that wired computer is running Ubuntu 16.04 (with a wired interface named enp1s2f3 — look it up via a command like ifconfig or ip address etc), I set its static IP address by adding the following to my /etc/network/interfaces:

iface enp1s2f3 inet static address 192.168.1.10 netmask 255.255.255.0 gateway 192.168.1.1 dns-nameservers 192.168.1.1

And then run sudo service network-manager stop to make NetworkManager cool its butt, and sudo service networking restart to use the static IP.

DD-WRT Firmware for TRENDnet TEW-812DRU Wireless Router

I'm lucky enough to get gigabit internet access at home, from Wave Broadband, with which I'm quite happy. And I don't even need a modem — with my apartment building, I can just jack directly into the Ethernet port in my living room wall. I originally got a Kasada router, but its firmware hasn't been updated in a couple years, so I decided to get a new router that I knew would be updateable with the Free Software DD-WRT firmware.

I got a TRENDnet TEW-812DRU v2, which although it's like 5 years old, is as fast as I need (supporting gigabit ethernet, plus 1.3 Gbps 802.11ac and 450 Mbps 802.11n wireless on separate 5 GHz and 2.4 GHz channels) — and a quarter of the price of comparable new routers. And, importantly, it looked like it was well supported by DD-WRT.

And it did turn out to be well supported by DD-WRT. Having first read through all the forum posts about the TEW-812DRU, I found that, unlike some other routers, you don't need anything special to use DD-WRT on the TEW-812DRU — just upload the new firmware to the router through its web UI and let it do its thing, no tricks needed.

So the first thing I did when I plugged in the router was login to its web UI and flash it with the "Open Source" firmware I downloaded from the TRENDnet TEW-812DRU downloads page. That turned out to be DD-WRT v24-sp2 r23194, compiled on 12/21/2013. I was happy it worked, but that firmware was just way too old.

So next I looked up the TEW-812DRU in the DD-WRT router database, and that prompted me to download something labeled DD-WRT v24-sp2 r23804 (but turned out actually to be r23808), compiled on 3/27/2014. I flashed that firmware through the web UI — but when the router rebooted, it presented me with an "Emergency Web Server" page. I went to look up what that meant via a working internet connection, and when I checked on the router again, the Emergency Web Server page had been replaced with the working DD-WRT web UI. I figure it must have just taken a little extra while for the router to boot everything up, no big deal.

But that firmware was also way older than I was hoping for, so I went searching through the downloads directory of the DD-WRT site — and finally found the latest version of the TEW-812DRU firmware here:

https://download1.dd-wrt.com/dd-wrtv2/downloads/betas/2018/07-16-2018-r36330/trendnet-812DRUv2/

I flashed that firmware through the router's web UI, and was very pleased to see the router reboot with no issues at all, happily running DD-WRT v3.0-r36330 mini — compiled just a few days ago on 7/16/2018. Finally, peace of mind that no bears, pandas, or kittens will be making themselves at home inside my router!