Intermittent wireless connection and disconnects with DD-WRT and Windows 7

If you’re using DD-WRT on your router you may find that certain wireless configurations cause the wireless clients to either be unable to connect or drop connection. This seems to be the most noticeable on Windows 7 systems, but likely happens on other systems as well. Note that I did not observe this at all on a Linux-based system and I’m completely unable to explain why. Perhaps a difference in the wireless stacks between Windows and Linux highlights this issue.

Issues related to this include not being able to connect to the wireless AP, instead receiving a message such as “The access point did not allow the connection” or something similar (Apologies, I don’t have the exact error message.), and losing wireless connection to the network or AP, even though it is still shown in the list of wireless networks.

This appears to be related to the wireless security settings, specifically the settings for security mode and WPA algorithm. See the following screenshot:

ddwrt_wpa_mixed

Having the security mode set to WPA2 Personal Mixed and the algorithm set to TKIP+AES appears to cause the problem.

According to the DD-WRT help:

WPA2 Mixed
This mode allows for mixing WPA2 and WPA clients. If only some of your clients support WPA2 mode, then you should choose WPA2 Mixed. For maximum interoperability, you should choose WPA2 Mixed/TKIP+AES.

So, according to this, it should work — but it doesn’t seem to work quite as advertised. Instead, this is the recommended setup as long as all your wireless clients support WPA2:

ddwrt_wpa

Security mode set to WPA2 Personal and algorithm set to AES only appeared to completely solve the problem.

For the curious, this is DD-WRT v24-sp2 (08/12/10) mega (SVN revision 14929), the current recommended build.

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  1. #1 by NMI on June 12, 2011 - 10:48 am

    Awesome work on figuring this out!

  2. #2 by Thomas Szteliga on June 13, 2012 - 4:15 pm

    Exactly the same here. On my WRT54GL with ddwrt all devices connected to those “additional” SSIDS with TKIP+AES got disconnected every few minutes, and after 1 minute the connection came back. Only the “main” SSID (was WEP) had no problems. So I will now try Your suggestion, by setting to AES, and we will see :-) Hope this helps, because a firmware upgrade did not :-) Thank You for this tip!

    • #3 by Mike Beach on June 15, 2012 - 8:27 pm

      You’re most welcome.

  3. #4 by Anthony McLin on June 18, 2012 - 9:09 pm

    If this solves the issues I’ve been seeing with my network for the past 2+ years, I owe you a beer.

  4. #5 by dynedain on June 18, 2012 - 9:09 pm

    If this solves the issue I’ve been seeing on my network for the past 2+ years, I owe you a beer.

  5. #6 by Joe Smith on January 25, 2013 - 10:05 am

    Same thing happening to me. Been having the problem for quite some time but didn’t bother me that much until I started working from home. Tried all kinds of stuff including switching channels, updating firmware and some other stuff on my Buffalo router running DD-WRT and nothin’. This happened to be the first hit on my google search and did the trick nicely. THANK YOU!

  6. #7 by fizie-sama on May 9, 2013 - 10:38 am

    was in the same boat as Joe. Thanks a zillion brah!

  7. #8 by Treah on June 16, 2013 - 9:54 pm

    Yeah this is compleatly a retarded windows problem and has nothing to do with DD WRT. WIndows broke tkip encyption a while back and continues to deny they did it.

  8. #9 by David on June 21, 2013 - 3:41 pm

    Wow, all my work computers running Windows 7 have had a hell of a time connecting to my home router running dd-wrt. I changed all sorts of settings on the machines and on the router but never figured to try this.

    I changed it and whoala! All my window’s 7 machines happily connected and stayed connected to the network! Finally!

    Thanks a billion for this tip.