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Tomato can't connect a weak client, DD-WRT can

Discussion in 'Tomato Firmware' started by etchie, Jan 3, 2011.

  1. etchie

    etchie Networkin' Nut Member

    Hello all,

    I have a weird problem with Tomato firmware.
    My set up is: WRT54GL v1.1 with 2 linksys hi gain antennas (7dB) located at the window. 1st laptop via wirelles in my house - signal "Excellent" or "Very Good". 2nd laptop in next house, distance cca 35 meters, signal usually "Low" or "Very low", most of time usable however connection sometimes drops. Used firmware was DD-WRT v24-sp2 which showed signal strength of 2nd laptop around -79. Ping from 1st PC to 2nd was about 3ms, packet loss during few hours was below 1% (ping -t).

    Now the problem: I decided to upgrade from DD-WRT to Tomato 1.28 because of great QoS capability but result was that 2nd laptop could not connect from its usual place at all. When I brought 2nd laptop into my house there was no problem with connection. After 2 days of manipulation with antennas and router position with no success I had to put back old DD-WRT and the weak client was back again. I tried to use TeddyBear modification based on ver. 1.28 with the same result as original Tomato.

    Question: is there any limitation in Tomato fw. for lowest acceptable signal strength ? Or what might cause this problem ? I suppose it must be in firmware cause nothing else was changed. Thank you very much for your help or advice.
  2. Toastman

    Toastman Super Moderator Staff Member Member

    Was DD-WRT's transmit power higher?
  3. etchie

    etchie Networkin' Nut Member

    Yes, in both cases I use/used 71mW.
  4. Toastman

    Toastman Super Moderator Staff Member Member

    They probably aren't the same between DD and Tomato. However, 71 is quite high, should be OK. You might like to look at this thread, there are some comparative graphs. I can't see any reason why the receiver should be any different, but the transmit power is always a variable. I trust you tried different countries? Some countries limit the power to quite low settings in the wireless driver itself. U.S. is usually OK.

  5. TexasFlood

    TexasFlood Network Guru Member

    You might also want to check the advanced wireless settings. I've seen some of these have an impact on the ability to connect and dd-wrt might have different defaults than tomato. I'm assuming you already checked the obvious like channel to make sure it's the same as that can definitely have an impact.
  6. etchie

    etchie Networkin' Nut Member

    I saved all settings from DD-WRT into html files before the update to Tomato. Then I mirrored all settings according previous ones. Tomato has some more settings - like Country selection. I set my country however I did not check "Obey regulatory power" checkbox. AFAIK, DD-WRT has no country selection or regulatory power settings. I will try the whole thing again whith country set to US as Toastman reminds in the previous post. Honestly, I did not try different countries. Maybe this makes the difference.
  7. etchie

    etchie Networkin' Nut Member

    Recent update:

    I put there Tomato 1.28 fw. and let it to use settings from previous DD-WRT setup. So, I haven't erased nvram. (during initial updates I had) Some parameters remained but some were set to default by the new firmware. E.g. transmit power was set to default value 42mW. But weak client was there ! Then I continued as before to TeddyBear's modification of Tomato and the weak client could not connect. I have not seen him among devices. I checked all parameters and corrected them if there was a different value. Country was set to US but weak client was not visible. Then I returned to unmodified Tomato 1.28 again without erasing nvram and weak client was back again just out of the box.
    So I have to correct/update my previous information.
    1. Tomato 1.28 sees a weak client as DD-WRT does
    2. Country setting was in modified Tomato
    3. problem remains with modified TeddyBear fw. (tomato-ND-1.28.8754-Std.trx)

    Probably during initial update to Tomato 1.28 my remote weak client was really off. Then I continued updating to TeddyBear's mod and I got impression that both Tomato version behave the same. Now the conclusion is that problem is just in modified fw.

    Thank you all for your advice and help. I will stay at Tomato 1.28 probably with tx power set to default 42mW instead of my previous 71mW.
  8. TexasFlood

    TexasFlood Network Guru Member

    I seem to recall reading previously that, at least with some newer versions of the wireless driver, some country settings have a side effect of silently enforcing regulatory power caps. I don't remember the details, maybe someone else here could comment. You could probably confirm it by testing. Use a tool, such as netstumbler, to watch the received transmit power from a client, then set the power to 20, 40, 60, 80, or whatever increment you want, and note the changes in received signal level. See where it levels off on Tomato, and potentially repeat on DD-WRT if you're motivated enough. DD-WRT could be either avoiding those country settings or simply using an old enough driver to completely avoid the issue. Not saying this -is- the cause of your problem, just a possible cause to check out.
  9. TexasFlood

    TexasFlood Network Guru Member

    If I'm reading correctly, are you saying that you did not do a complete NVRAM reset after loading Tomato over DD-WRT? FYI, the official Tomato FAQ recommends - 'If you upgraded from another firmware, a complete reset is recommended. Go to Administration/Configuration and select "Erase all NVRAM..." after installing Tomato.' And based on my experience, I agree and definitely recommend the reset. NVRAM variables and what they do vary considerably between different firmwares and can have unpredictable results if not cleared. If I misunderstood your post then...NEVER MIND, :wink:.

    So you're saying the official Tomato doesn't have the country setting and your weak client works but not with the "enhanced" builds, like Teddy Bear, which do have the country code setting? If this is true then it probably has to do with a newer wireless driver, OR you didn't find the right country setting, OR could be a side effect of not doing an NVRAM reset if you didn't.

    IIRC, the default is Japan, and either Japan, USA or Singapore were some of the better choices for higher power. I personally don't know what impact these have on the regulatory power cap. I always use the default of 42mW so it makes no difference to me. The default of 42mW works fine for me. Coincidentally I had been using 42mW for TX power, based on my own testing, for some time before Tomato starting using it as the default.. Perhaps proving that 42 is, in fact, the answer to the ultimate question of life, the universe and everything?

    At any rate, looks like you have found a solution, to run the official Tomato build which works for you. I just can't help but wonder about the questions your raised. I might do some tests if I ever get time. I don't have any router with official Tomato right now, mine are either Teddy Bear or RAF, so will have to reflash at least one to test.
  10. Toastman

    Toastman Super Moderator Staff Member Member

    Actually, if the default Japan setting is used, normally that sets the router to use a rather low power and it can't be increased further. The US setting is always a pretty safe bet because we know it allows the increase of transmit power. You absolutely MUST erase NVRAM and reconfigure after changing firmware. The majority of the weird things people experience after upgrading firmware are due to this one omission. See to this before doing anything else.

    What is interesting is that on this installation, he's saying that on a marginal signal the earlier driver (??) can detect his remote laptop but the later one can't, that is - the sensitivity of the receiver is different with the later drivers. I've never noticed this before but it's possible, as none of us have ever been looking for this. I just tried it here, but they seemed pretty much the same though.

    If it were me, I'd use the known-to-work US country setting, a transmit setting of 150 to make sure the laptop can hear the router (which is what all my systems use). Then I'd ring all the changes of the rather less obvious settings in the TX setup page to see if one of them is affecting the receiver. Usually the defaults shown with a * work fine but maybe something got changed. I'd repeat the tests on channels 1, 6, 11 to see if they were any different.

    Here are the settings I just used here on Tomato Firmware v1.28.8754 ND USB Std on a WRT54GL. Wireless driver is v With these settings I can't see any big difference between the firmwares, the weak AP's on a distant block of flats is still detectable at around -92/95 dBm. BTW - there is no "obey regulatory power" checkbox - what version was that in?

    Afterburner disable
    AP isolation disable
    Authentication auto
    Basic rate default
    Beacon int 100
    CTS protection disable
    Regulatory mode OFF
    Country United States
    Bluetooth coexistence disable
    Dist/Ack Timing 0
    DTIM int 1
    Frag Threshold 2346
    Frame burst disable
    Multicast rate auto
    Preamble long
    RTS thresh 2347
    RX/TX ant auto
    transmit power 150
    Interference Mitigation None
    WMM disable
    No Ack disable
    APSD mode disable
  11. etchie

    etchie Networkin' Nut Member

  12. etchie

    etchie Networkin' Nut Member

  13. Toastman

    Toastman Super Moderator Staff Member Member

    Good luck!
  14. TexasFlood

    TexasFlood Network Guru Member

    I noticed that but neglected to comment on it. The way it was worded, "Tomato 1.28 sees a weak client as DD-WRT does" seems to imply increased sensitivity. But I'm not going to jump to conclusions since I already misinterpreted a post in this thread. Perhaps what was meant was simply that the client was able to connect with official Tomato 1.28 which could be due to marginally increased TX power or another yet unidentified factor.

    Apparently I misread your earlier post. My bad.

    Indeed. Good luck!
  15. Toastman

    Toastman Super Moderator Staff Member Member

    I was going by this:

    All my WRT54GL's are able to see AP's at around -93/95 from over a kilometer away, no matter what firmware I run.

    Anyway, can't think of anything else. Hope it works out!
  16. TexasFlood

    TexasFlood Network Guru Member

    Good point.
    Doesn't make sense does it? Different drivers maybe, but your experience doesn't seem to back that up.

    Position of the routers can also make a big difference but I'm assuming this did not change.

    When I do scans here, the time of day, weather, and interference such as microwave ovens, bluetooth, etc all make a difference to weak signals. My scan results vary CONSIDERABLY over time with regard to how many weak signals get picked up.

    Anyway, I digress into rambling thinking out loud.
    I can't really think of anything else either and hope it works out as well!
  17. etchie

    etchie Networkin' Nut Member

    Hello all,

    the mystery is solved now. It was neither nvram issue nor new driver. Even it wasn't any country settings. It was actually a feature. :) TeddyBear's firmware contains some parameter in settings, which is not in DD-WRT nor in ordinary Tomato. Now I know I should paid more attention to this setting. But this one was new to me so I left it in its default value. Later, as mentioned, I was impressed by other improvements like QoS etc. and I evidently oversaw importance of this parameter. Here we go, its name is "Interference Mitigation" and is placed in Advanced wireless settings almost at the bottom (I know, it's not an extenuating circumstance). Default option is "WLAN Manual" and this is only mode in which weak client is not visible, i.e. cannot connect. All others worked for me. Case solved.

    Thank you for your useful advices and for your help. I hope this "research" helps somebody else in the same troubles. Maybe changing the default value to "None" in future releases would help as well. It's just a proposal to have more out-of-the-box firmware.
  18. etchie

    etchie Networkin' Nut Member

    One more thing I'd like to share with people here. Because during this process I played with flashing of different firmware without and with NVRAM erasing, it may give a wrong conclusion that it does not matter about it. Because finally my device worked and nvram was not the issue. But here are my latest observations:
    when nvram is not erased after flashing the result might be (significantly) less of free nvram - though, this is usually obvious and we would expect it
    second negative thing are wrong default values, not all, just some; most tricky are inactive default values (grayed) because after activation of a feature’s check box we can tend to return to these values if something does not work; actually the same might concern all default values
    third observed and not so obvious thing is amount of free RAM - in my case a difference was about 1MB. When nvram was not erased properly free RAM was hardly 500kB. But the same configuration and the same activated features or services after nvram properly erased, resulted in about 1,5MB of free memory. (counting of cache and buffers as free memory was switched off so it have not affected my observation)
  19. TexasFlood

    TexasFlood Network Guru Member

    Just to add my personal experience... This experience is dated, I must say as I have religiously done NVRAM resets for a LONG time except when doing minor updates of the same firmware build. probably 8 or 9 times out of 10 you can get away with not following the "best practice" of a full NVRAM reset. As etchie stated, at minimum you'll lose some NVRAM space and have some incorrect default settings. But above and beyond that, you can run into issues which I can only describe as weird or spooky. LIKE, WDS just won't work, periodic disconnects, wired connections work but not wireless or visa-versa. I saw other such issues but can no longer recall. Since I started following what I consider to be a "best practice" of doing a full reset when either switching builds or a major upgrade, I have seen few, maybe none(?) issues that could not be explained.
  20. TexasFlood

    TexasFlood Network Guru Member


    Thanks for the info.

    I admit that I'd never noticed that setting and mine is at the default setting of "WLAN Manual". In the TomatoUSB Documentation » Web GUI reference guide » Advanced Wireless Settings, there is a brief description of this setting.

    Apparently it's available on all builds from a shell using the "wl" command with the "interference" argument, choices being 0 = none, 1 = non wlan, 2 = wlan manual 3 = wlan automatic. TomatoUSB actually put it in the GUI unlike most, if not all other builds. Basically looks to me like it's "filtering" or ignoring weak "interference" AKA signals :wink: of other APs. Sounds like a side effect is also causing your weak client to be ignored.

    I don't have an official Tomato 1.28 loaded right now so I can't check but might be interesting to telnet/ssh into one and run "wl interference" to see what it's set to and if it really differs from TomatoUSB.
  21. Toastman

    Toastman Super Moderator Staff Member Member

    Great that you found it. Being of an unusually suspicious nature, I always turn "features" off until I see a need for them. This was one such feature. Does it ever do anything useful, I wonder?

    Happy New Year!
  22. occamsrazor

    occamsrazor Network Guru Member

    On my E3000 with latest Victek build, the default for Interference Mitigation is "WLAN Auto".... just FYI.
  23. TexasFlood

    TexasFlood Network Guru Member

    I just checked my Victek RAF router and it is also set to auto by default, running "Tomato RAF Firmware v1.28.8515 _RAF ND Std". My TomatoUSB router defaulted to "WLAN Manual" so I'm thinking of playing with that setting a bit now that I know it exists, :wink:.

    Doesn't look like there is a way to permanently change this but could always put an entry in the admin->scripts init tab to change it, like this to turn it off:
    sleep 5
    wl interference 0
    Again, where the numeric parameter choices are:
    0 = none
    1 = non wlan
    2 = wlan manual
    3 = wlan automatic
    Not sure if the sleep is needed, maybe not, just being cautious.
  24. mstombs

    mstombs Network Guru Member

    stock, original driver version

    Tomato v1.28.1816
    BusyBox v1.14.4 (2010-06-27 20:11:16 PDT) built-in shell (ash)
    Enter 'help' for a list of built-in commands.
    # wl ver
    wl:     3.90 RC37.0
            wl0: Feb 24 2005 20:22:09 version
    # wl interference
    Auto Wireless LAN Interference mitigation is enabled and not active
  25. etchie

    etchie Networkin' Nut Member

    Since returned value of wl command is descriptive only, please try "nvram get wl0_interfmode". This one returns a numeric value. There is also wl_interfmode parameter there but this one is not affected by changes in Interference Mitigation drop down box in GUI.
  26. adlerfra

    adlerfra LI Guru Member

    I am running RAF1.28.8617 MIPSR1_RAF K26 Std on my WRT54GL. Default setting for Interference Mitigation is "WLAN Manual". I measured the wireless Noise Floor several times (under the Devices Section) and it was -92 dBm +/- 1 dB. I then changed Interference Mitigation to "WLAN Auto" and remeasured the noise floor. It decreased to -98 dBm and has stayed at that level +/- 1 dB after subsequent measurements.
  27. mstombs

    mstombs Network Guru Member

    Those vars not in this old driver stock Tomato

    # wl interference -h
            Get/Set interference mitigation mode. Choices are:
            0 = none
            1 = non wlan
            2 = wlan manual
            3 = wlan automatic
    But it clearly defaults to 3 auto:-

    # wl interference 0
    # wl interference
    All interference mitigation is disabled.
    # wl interference 1
    # wl interference
    Non-wireless LAN Interference mitigation is enabled.
    # wl interference 2
    # wl interference
    Wireless LAN Interference mitigation is enabled.
    # wl interference 3
    # wl interference
    Auto Wireless LAN Interference mitigation is enabled and not active
  28. TexasFlood

    TexasFlood Network Guru Member

    Thanks mstombs.

    My Victek Tomato RAF router showed "enabled and active" when I first looked at it. As a test I reboot it and it came up initially as "enabled and not active" although I assume it would very likely kick in at some point. etchie, sounds like yours is also set to auto therefore could get enabled if the router "sees" other wireless APs transmitting, so if you lose visibility to your weak client at some point, that could be the cause.

    Again, the TomatoUSB Web GUI reference guide for Advanced Wireless Settings describes Interference Mitigation as:
    Interference Mitigation
    Sets the Wireless Interference Mitigation mode. Select "None" if you have no other electronic devices around that may cause an interference. Use "Non-WLAN" if the primary source of interference in your area are non-WLAN electronic devices, such as cordless phones, microwaves etc. The default selection - "WLAN Manual" - activates interference mitigation against other Wireless LAN APs. "WLAN Auto" is similar to "WLAN Manual", but it only activates mitigation if it actually can see other wireless APs transmitting at the moment. It seems that the default "WLAN Manual" selection works better in most cases.

    I have interference mitigation disabled on all my routers right now as a test to see if I notice any pros/cons.
  29. etchie

    etchie Networkin' Nut Member

    I'm currently using Interference Mitigation in "None" mode. But thank you for pointing out difference between Manual and Auto modes. Manual mode did not work for me as we know. Auto mode did. But definitely it was only in its initial and inactive stave. As soon as it would detect other APs, its mode would change to "enabled and active" state and I would wonder where is my weak client again. Because "enabled and active" equals "Manual" by my opinion.
  30. TexasFlood

    TexasFlood Network Guru Member

    I would agree that for all practical purposes "enabled and active" equals "Manual". Unless, of course, auto disables Interference Mitigation if no longer needed - I don't know if it does or not so would assume not unless proven otherwise. At any rate, I think you did the safe thing by disabling. You can always turn it back on if you suspect interference right?
  31. TexasFlood

    TexasFlood Network Guru Member

    Didn't notice any real issues running with interference mitigation off for a few days. Then as the day when on today, my wireless performance went to hell. Re-enabling interference mitigation to WLAN manual improved it a lot. Interestingly I then tried Non-WLAN and that seems as good if not better. Guess I can't really judge right now, will have to wait until tomorrow same time period as things got bad today and see what happens then. Not sure why I didn't notice this before, either I wasn't really testing it or something new was just flattening me today.
  32. Toastman

    Toastman Super Moderator Staff Member Member

    I've also been playing around with it, just to see what would happen, as I have up to 30 odd AP's on some sites. Probably if we were able to examine what was going on on the band with a spectrum analyser, it would be immediately apparent what it did. But TBH, so far I'm rather apt to turn it off. It seems to be somewhat unpredictable. With it on, quite often people aren't connecting to an AP right outside their room, but often connect to one a long way off with low throughput - whereas I expected the opposite to happen.

    I believe a lot of people's problems lately may quite possibly be caused by auto channel selection and interference mitigation default settings. Auto channel often placing people on odd channels where they get interference, and the mitigation makes the things somewhat deaf.
  33. Beast

    Beast Network Guru Member

    Using wireless survey::

    I have noticed that every time i switch to Teddybear USB build 24k versions. I can only see one or two wirless clients out there in the neighbor hood. But when I switch back to Toastman's build ( which is what i just did) I can see seven to eight clients out there. And that is with default settings after an nvram clear. I always thought it was do to Teddybear using a newer wirless driver.

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