Setting up multiple WLANs in DD-WRT

DD-WRT K2.6 Kernel vs. K3.x and How To Upgrade 24


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.

  • Denys Pavliv

    Hi there! thanx for this article! But, I have a question – can’t find any K3.X for E4200, but some people on DD-WRT forum report that they run K3.X on E4200… Can you help with link to DD-WRT K3.X firmware for Linksys E4200?
    Thank you in advance!

  • Thomas Jose

    Hi Steve,

    Nice blog post! I am having issues with any of the K3.x firmwares. The problem that I am having is my overall speed is slower when compared to using a K2.6 firmware.

    When using a K2.6 firmware my speed is approximately 85/85. When using a K3.x firmware my speed goes down to 70/50.

    (Speeds were tested with http://www.speedtest.net)

    Keep in mind these speeds are tested on a wired connection. After seeing the speed drop I figured it wasn’t worth testing wireless.

    I have followed the instructions for upgrading (do 30-30-30 first…etc) and tried different K3.x builds including the latest build as of this post v28211.

    Any ideas to why there is a speed drop with K3.x kernels?

    (Sorry, posted this on your original E4200 blog post but looks like my comment disappeared there)

  • Pingback: My Cisco Linksys E4200 DD-WRT Settings for Max Speed()

  • It might not be available… as it might not fit. The K3.x needs more room, and so some pkgs aren’t there. 🙁

    • Andrea Verocio

      Thanks, as i suspected. I’ll stick with the latest Kong ?22000??++ for now. As long as there are no blaring security issues ?

      • Nope. Heartbleed was the biggie, and that’s fixed in the ++ version.

        • Andrea Verocio

          Ty bud, your the best!

  • Gaudi

    Hi Steve, can you recommend a version for an old WRT610N v1?

    Thanks! !

  • Great question. Yes, I would always use a trailed build if moving from K2.6 to K3.x.

    • William Harris

      Thank you for the quick reply. Would you recommend flashing the non-trailed building immediately after flashing the trailed build when upgraded from K2.6 to K3.X? I’m not sure what I lose by keeping the trailed build in this case.

      • Nah. There’s no difference when running the trailed vs. non-trailed build. The only difference is that the trailed builds have special additional info to load properly. But once it’s loaded, you’re good to go. 🙂

  • Gaudi

    Thanks Steve. I have found some 20805 or so that is the newest recommended, but wanted to check if there was a k3.0 available.
    Will stick to the one I have then.

    • Well it DOES have the 8MB flash, meaning it could handle the size of the file. I know the v2 WRT610N will take a K3, but I don’t know about the v1.

  • PDK

    Are you still staying with K26 on the E4200’s?

  • Dave

    Steve,

    Thanks for putting all of this together. It helped a great deal.

    I have installed K3.x on the E4200 and now realize I don’t have DLNA.

    Is it possible to go from K3.x to one of the Kong builds with DLNA?

    thanks,
    Dave

  • Paul

    Hi Steve,

    What is the SAFEST downgrade path from K3.X to
    K26 DD-WRT builds, (same for revert back to stock firmware from either one) after trying out the K3.x builds. I
    found k3x slower at LAN level but WiFi works fine. I tried different
    scenarios to improve LAN throughput but all failed. I remembered k2.6
    always met speed expectations. I am using linksys e4200v1.

    Thank you in advance for your quick reply!

    Paul

  • GB

    Hi Steve

    please could you tell me the exact model of your Ubiquity Edgerouter you own. The reason is that I wanted to get one enough fit and cheap for my small condo (LAN+wan+wireless). I wanted to replace my old e4200 running 27739 k2.6 firmware (the poor LAN throughput is killing me for years….)

    Thanks Steve for your quick reply!!!!

    • You bet! I have an EdgeRouter Lite (ERL-3) with a UAP-PRO-AC WiFi antenna.