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RT-N16 + Shibby v107 - WDS+AP 40MHz channel width not working

Discussion in 'Tomato Firmware' started by tievolu, Aug 16, 2013.

  1. tievolu

    tievolu Network Guru Member

    I'm having an odd problem with my setup. Currently I have two RT-N16's configured as AP+WDS on channel 1, 20MHz width, using WPA2-AES. This all works fine.

    I want to try and maximise the bandwidth by switching to a 40MHz channel width, but when I set this in the Basic wireless settings on both routers (Lower control channel), the actual link is unchanged, and continues to use a 20MHz channel, even after a reboot. I've checked the relevant parameter in nvram and it looks correct (wl0_nbw=40), so why is it being ignored? Is it simply not possible to use a 40MHz channel width in an AP+WDS configuration? Is there a technical limitation involved?
     
  2. mvsgeek

    mvsgeek Addicted to LI Member

    Can't comment on Shibby 107, but Toastman 0502.8 works as expected with the same settings - AP+WDS, Channel 1, Lower, WPA2-AES, Mode N (or Auto). InSSIDer shows a 40MHz channel width, which of course drops to 20MHz if the mode is changed to G.
     
  3. tievolu

    tievolu Network Guru Member

    Just out of curiosity, would a G client associated with either of the AP's cause the bandwidth to drop to 20MHz? My GF has a older phone that can only do 802.11g...
     
  4. mvsgeek

    mvsgeek Addicted to LI Member

    I think so, but others with definitive knowledge may confirm or refute. You could try setting both routers to 'N Only' and see if InSSIDer shows 40MHz.
     
  5. Monk E. Boy

    Monk E. Boy Network Guru Member

    With 40Mhz 2.4Ghz channels you can only have 1 AP, and only one AP, because it uses 2 out of the 3 available channels (1 and 6 or 6 and 11). By setting up two APs with 40Mhz channels you'll have guaranteed interference on channel 6.

    And since you're relying on the wireless link to maintain your network (WDS) having an intermittent connection may not work out very well.
     
  6. tievolu

    tievolu Network Guru Member

    Ok, so is it automatically backing off from the 40MHz configuration due to the "interference" on the second channel?

    I'm happy to continue using a single 20MHz channel if it's going to be more reliable (I suspected it would be anyway). I'm just curious as to why the 40MHz setting doesn't seem to take effect at all.
     
  7. Monk E. Boy

    Monk E. Boy Network Guru Member

    I don't think it would back down, but I don't use WDS so I can't say for sure.
     
  8. tievolu

    tievolu Network Guru Member

    I found the solution by pure luck after messing about with some settings.

    Some time ago I had my region set to JAPAN (in the advanced wireless settings) to experiment with use of the higher channels that aren't available in the UK. I changed this back to UNITED KINGDOM and now the 40Mhz setting takes effect as expected. I can keep it this way as channel 1 has the least interference for me anyway.

    So problem solved, but I'm not sure if this behaviour is correct...
     
  9. Marcel Tunks

    Marcel Tunks Networkin' Nut Member

    That's correct. The Japanese regulations are more sensible for urban areas. 40MHz channel width and higher transmission power creates an unfriendly wireless environment in densely populated areas.

    Sent from my Nexus S using Tapatalk 4
     
  10. tievolu

    tievolu Network Guru Member

    Cool, well that's a good thing to know. I hope this thread is useful for others. I certainly wasted a decent chunk of time tracking the problem down :)
     

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