For the past while, I’ve recommended DD-WRT K2.6 firmware builds for the Linksys E4200 router, as well as other Linksys / Cisco WiFi routers. The builds based on the newer K3.x Linux kernel have now reached a stable enough point where you can run them… but I still recommend the K2.6 builds because they are much faster according to my tests.

However, if you’re convinced you want to try out the K3.x builds anyway, this article contains important information on how to safely migrate from a K2.6 DD-WRT build to a K3.x one.

I’ve always recommended a “30-30-30” reset (holding down the reset button for a total of 90 seconds: 30 with the power plugged in, 30 seconds unplugged, then 30 seconds plugged in again) between every firmware update, but the truth of the matter is that it’s been possible to get away without doing it on the “later” DD-WRT builds. That’s still the case if you’re going from a DD-WRT K2.6 build to newer K2.6 build, or even a K3.x to another K3.x build, but if you’re making the jump from a DD-WRT K2.6 build to a K3.x build, you must do the 30-30-30 reset first. No exceptions. Failure to do so will result in strange behavior, settings not being saved, and just general wonkiness.

Also note that you cannot use the “Backup Settings” feature in the DD-WRT Administration / Backup tab to save your settings from a K2.6 build and restore them on a K3.x build. Again, you’ll have problems. I know this is a bummer, but your best move is to go through all your tabs and take screen shots of the non-default settings (and if you don’t know what the default settings are, just screen-cap them all), do the 30-30-30 reset, upgrade to a K3.x kernel, then manually re-configure your router.

Why Upgrade from DD-WRT K2.6 to K3.x?

As for what features are available in the K3.x kernels vs. the K2.6 ones, you can browse a discussion on this topic on the DD-WRT forums. But the TL;DR version is:

• Support for newer USB hardware, such as drives with 4K sectors
• Support for additional and updated file systems
• Optimizations for solid state drives
• Newer congestion algorithms
• Security fixes that come with the Linux K3.x kernels (since Linux K2.6 is no longer being developed)
• Support for additional routers (including those with up to 64K of NVRAM)
• Some reports say improved media streaming (not confirmed)

But the most compelling reason people want to to move from the K2.6 kernel to K3.x is that the majority of DD-WRT development is now being focused on the K3.x builds. If you have an older router and are happy with your K2.6 build, there’s no harm in staying there. But if you want to be on the “bleeding edge,” you’re going to need to move to K3.x eventually.

And when you do, don’t forget to 30-30-30. Zero exceptions. You might try it and think you got away with it, but you’ll eventually have to reset everything to avoid strange behavior.

Also, when moving from a K2.6 build to a K3.x, I recommend flashing a “trailed” K3.x build.

Reasons Not To Run DD-WRT 3.x

If any of the following apply to you, you’re better off staying with the K2.6 builds:

• You have an older router that doesn’t have enough RAM to fit a K3.x build. If you’re got an old-school WRT54GL, just stick with an old and stable K2.6 build of DD-WRT.
• You have an older router that doesn’t have a fast processor, which means that even if a K3.x build will fit into your router’s RAM, it will run slower on K3.x that it does on a K2.6 build. This should get better as the K3.x builds get more efficient, but there are no guarantees. As of right now, according to my tests, the K3.x builds are still way slower for both wired and wireless.
• You need packages that aren’t included in the K3.x build due to space constraints. The K3.x kernel takes up more RAM than the K2.6, so some packages are left out.

As to which packages are and aren’t included, that’s always in flux… so the minute I type a list here, it would be outdated. The best way to verify which packages are installed are to check in the DD-WRT forums, or simply install it and see if it has everything you need. If it doesn’t, then do a 30-30-30 and go back to the K2.6 build.

To find the latest beta builds of DD-WRT (including both K2.6 and K3.x builds), visit the Other Downloads section of the DD-WRT.com website, or the DD-WRT FTP Beta Site.

You can always find my latest recommended stable K2.6 and K3.x builds for the Linksys E4200 in this article.