By Aaron Weiss
July 07, 2006
You tried an open source firmware upgrade, and all you got was a lifeless router. Here’s how you can fix it. Maybe.
- Ask the Wi-Fi Guru
- How to: Build a Wireless Bridge Using DD-WRT, Part II
- How to: Build a Wireless Bridge Using DD-WRT, Part I
- Introduction to NetStumbler
- The Open Source WRT54G Story
One of the more exciting developments for networking enthusiasts has been the evolution of open-source firmware replacements for certain popular, inexpensive routers (usually the famed Linux-running Linksys WRT54G).
While replacement firmware offers the promise of significantly expanded features, greater customization and mondo-tweakability, it also carries some risk. Should misfortune strike, you might, oh, let’s say, render your router into a useless hunk of plastic. Or, as victims prefer to say, you could “brick it.” How does a router become a brick? And if it does, is there any hope of bringing it back to life?
The short answers: “by accident,” and “yes… sometimes.”How a Router Becomes a Brick
Bricks are very good at holding up the walls of your house. Bricks are not very good at routing network traffic. You don’t want your router to suddenly become one. (Likewise, you don’t want the bricks in your walls to suddenly become routers – although that would be pretty cool, no?) But sometimes it happens. Often, you can avoid this fate by understanding how a router can become a brick.
There is an alchemy to turning a router into a brick. The most common formula is the bad flash. When you upgrade the firmware in your router, you’re basically swapping in a new brain in place of the old. This brain controls most of the router’s cognitive functions.
The upgrade process, described in The Open Source WRT54G Story, can require up to two minutes. If “Something Bad” happens during this process – loss of power to the router, loss of network connectivity to the uploading PC – you may have just bricked your router.
When upgrading your firmware, try to prevent “Something Bad” from happening:
- Be sure the power source is secure.
- Only upgrade through a wired Ethernet connection; do not use a wireless connection.
- Be sure to manually configure the IP address on your uploading PC – do not rely on automatic DHCP address assignment.
- Be sure to disable any software firewall running on your uploading PC, including the Windows firewall.
Your router has a small amount of on-board NVRAM , or non-volatile memory. Sometimes your flash upgrade will be successful, but your NVRAM will become corrupted. Often, this happens when the firmware you uploaded to the router wasn’t exactly the right version for your model. Be sure to read the upgrade instructions for your chosen firmware very, very, very carefully.
For example, consider DD-WRT, one of the most popular open source firmware replacements for Linksys WRT series routers. DD-WRT is available in many flavors. There is a “minimal” build with only a base feature set. There is also a “generic” build which lacks optimizations, and some model-specific builds, among other variants
When upgrading the router from the Linksys-branded firmware, you are supposed to “step up” by first installing the minimal DD-WRT build, and upgrading from there to a more feature-rich build.
However, when upgrading your router through DD-WRT’s Web interface, you’re directed to use the generic build.
Trip up on one of these finer points, and your upgrade may appear successful at first. But then you configure the router, it reboots, and hello Brickville, city of bricks. Most likely, your “successful” flash upgrade produced corrupted NVRAM.
You will always find message board threads by those who have disobeyed the upgrade instructions without dire consequences. These people can also eat pizza for three meals daily and never gain weight, and smoke a pack a day until they’re 98 years old. In fact, they often smoke and eat pizza while upgrading their routers. But the rest of us – we’re not like them. Just follow the instructions, carefully.