WRT54Gv2 won't hold wifi signal

Discussion in 'Tomato Firmware' started by garyfritz, Sep 17, 2011.

  1. garyfritz

    garyfritz Addicted to LI Member

    I have an old WRT54Gv2 that I've been running Tomato on for several years. It has always been a little bit flaky (my kids complain about weak/dropping connections all the time, but I never had any trouble with it) but it worked.

    Until now. Suddenly it's gotten worse. Sometimes you can get a connection, but then it'll drop it in a few minutes. Other times you can't connect to the wifi at all, even sitting right next to it.

    This may be related to another wifi router (Netgear) in the same room. We use one wifi for the kids, one for the adults. It *seems* that if I unplug the adult router, then the kid router works OK, but it's flaky enough I'm not sure. They're on separate channels, 6 and 11 if I remember right.

    I've upgraded to the latest 1.28 firmware. I did a full 30-30-30 reset as described on the DD-WRT site. It's still not working.

    Is there something obvious to try, or is this old box just dying on me?

  2. Toastman

    Toastman Super Moderator Staff Member Member

    It sounds very much like wireless interference. It may likely be the Netgear router that is the source, it may be too close to the WRT - (it needs to be several meters away). Or it may have jumped to the same channel as the WRT. I'd first of all install InSSIDer and take a look to see if there's anything obvious happening. Try variations on CH1, 6, and 11. etc. I wouldn't suspect the hardware just yet.
  3. garyfritz

    garyfritz Addicted to LI Member

    The Linksys had been within 20cm or so of the Netgear, but I already tried moving the Linksys to the next room, about 10m away. No change. It's currently about 2m away.

    I installed inSSIDer and, hm. A neighbor's wifi is on the same channel as the Linksys. It's 20-30dB below the Linksys signal, but maybe that's enough to interfere?

    The Netgear is on 11. The Linksys is on 6. Neighbor wifis are on 6 and 10, with weaker signals on 1 and 6. I tried moving the Linksys to 1 (far from Netgear) and 2-5 (no other signals), with no change: try to connect to the wifi and it almost instantly fails. I left it on 2.

    I tried to move it to 14 but it didn't seem to "take." Tomato accepted the change and it shows 14 if I replot the config page, but inSSIDer says it's still on 1. But it's disappeared from the 2.4GHz Channels amplitude map and I don't see the SSID broadcast.

    Hm. Odd. I was sitting right between the two routers. Not only was I unable to connect to the Linksys -- I couldn't connect to the Netgear either. When I tried the Linksys, Windows said "Windows cannot connect to network XYZ." But try the Netgear and it just said "Windows cannot connect to this network." Interference I guess? I went back to my office (one floor down, 2 rooms over) and then I could connect to the Netgear but still not to the Linksys.

    Thanks for your help! Any other ideas?? :)
  4. Toastman

    Toastman Super Moderator Staff Member Member

    If another router is on the same channel then whichever router is sending will take priority, and the other will wait for it to finish.

    Unless you have Japan set as country, you usually can't use channel 14. Also there's a good chance your PC won't use it anyway. Probably why inSSIDer is lost in limbo...

    Set to Singapore to get channels up to 13 with ability to change to higher powers. But usually best to stick to 1, 6, 11

    Don't forget you can also try putting both on the least congested channel (1?) - it may still be quicker if interference is less.

    Don't forget that there are many types of interference that will not show up with InSSIDer. But anyway, you know a bit more now about what to look for.

    There is a setting in Advanced/Wireless called "interference mitigation". I always set it to "off" for best throughput and signal strength but you may find it helps - try the different settings.
    xen0exe likes this.
  5. garyfritz

    garyfritz Addicted to LI Member

    I'm confused. Why stick with 1, 6, 11 if that's where everybody else is?

    Changing channel to 1 - 6 doesn't seem to help the Linksys. That indicates it's unlikely to be interference, doesn't it?

    The Linksys is being stubborn (again) and I can't connect to it via external LAN. I suspect it's reset its WAN address again. But it's after 11pm and I don't feel like dragging my laptop up to the routers for the 3rd (4th?) time today so I'll poke at this again tomorrow...
  6. Toastman

    Toastman Super Moderator Staff Member Member

    Why 1,6,11 ?

    Essentially it is because a wifi signal takes up more than 4 so-called "channels" on the band. Therefore there are only 3 non-overlapping groups of 4 channels available for WiFi use.

    This 2.4GHz band is not intended just for wifi but is shared with many other things that have smaller bandwidth and may only use 1 "channel".


    OK, let's suppose you are on channel 1 and so is someone else. Your gear is using the channel to transmit. His gear can decode your signals, knows it is a data transmission, and waits politely for it to stop sending before sending itself. That's polite channel sharing and that is what is SUPPOSED to happen.

    Now imagine you move on to channel 2 or even 3. Now his receiver cannot decode your signal although it is actually transmitting quite a strong signal on channel 1 (HIS channel). Since it cannot decode your signal, so it doesn't know it is a data transmission, and will start transmitting. As will yours. And now both of you are jamming each other.

    This is why you should not use intermediate channels.

    Now - to show you just how easy it is for things to be screwed by everyday consumer items on the same shared band, here are some real-life examples of what can happen - and there's no way to detect them with InSSIDer or other simple tools. I think you will understand from this that WiFi is a notoriously unreliable system, and when it doesn't work well there is no easy way to know WHY.

    1) Neighbor has a router less than 1 meter away on the other side of an apartment wall, running N wifi.

    2) Wife plugs in wireless baby alarm in bedroom next door.

    3) Apartment owner installs a wireless security camera outside your apartment.

    4) Microwave cooker(s) .... anywhere ... and usually many of them...

    5) Bluetooth devices such as phones, cameras, printers, that you aren't aware are even transmitting.

    6) Wireless mouse.

    7) Local doppler radar security system.

    In your case the problem seems to be connected with your Netgear router. You have to figure out how. You also seem to have an instability problem if the router keeps resetting addresses or whatever. I would sort that out first, erase NVRAM and set up again from scratch by hand.
  7. garyfritz

    garyfritz Addicted to LI Member

    Interesting. I suspected the 4-wide signals based on the inSSIDer display. Why on earth did they design this with wide signals, and narrow channel assignments that make most of the channels unusable!?

    Here's a channel survey from my office:

    Linksys 1 -68dB
    Netgear 11 -70dB
    Neighbor#1 6 -91 - 98
    Neighbor#2 10 -89 - 95
    ?? #3 11 -92
    ?? #4 1 -92
    ?? #5 6 -92
    ?? #6 11 seldom seen, and only from upstairs near the routers
    ?? #7 9 seldom seen, and only from upstairs near the routers

    It's odd that there is a strong(ish) neighbor signal on 10 (#1) and weaker ones on 11 (#6) and 9 (#7), and yet I have no trouble connecting to the Netgear (on 11) from my basement office. My wife is 2 rooms away from the Netgear and can usually connect OK but she says it's sometimes slow, though she hasn't characterized it.

    For some reason #3-#7 don't usually show on the 2.4GHz Channels display. Oddly enough I've never had any trouble receiving the Linksys from my office, but my sons (1 and 2 rooms away) always have -- which I always assumed was due to metal furnace plenums blocking the signal to their locations. But I just carried my laptop in there and the Linksys signal is STRONGER in their rooms than in my office. They're gone today but I'll install inSSIDer on their computers when they get back. But assuming this is an interference problem, the strength at their receivers may be less important than the strength at the transmitters -- ours, and our neighbors'. I.e. can the transmitters see each others' signals properly and step aside? Or are they stomping on top of each other?

    So since my Netgear is on 11, and two neighbors are on 6 & it's having trouble there, and there's only one signal on 1, it appears that channel 1 is the best choice for the Linksys. Still doesn't work there, though.

    BTW most of the interference cases you listed are reasonably unlikely here. This is a freestanding house, not an apartment. There are only 7 houses within about 200m. Nobody has baby monitors as far as I know, nor security cameras. Microwaver cookers would be very intermittent, especially with so few houses in the area. I think the only bluetooth devices within 30-40m are our cellphones, and I just tried turning them off -- no joy. Don't think we have any wireless mice either.

    I connected to the Linksys on one of its internal ports and checked its config. Its WAN address is set properly, but I can't seem to ping it from the outside, connecting to its "Internet" port and pinging its WAN address. I don't know why. I could yesterday. I'm getting more suspicious of it. I already cleared the NVRAM yesterday (that's what the 30-30-30 reset does, right?) and that didn't help.

    Arghgh!! I've spent half my weekend chasing this #$)!@# thing. I'd just give up and buy a new router and pitch the Linksys if I thought that would solve the problem. But if it's an interference problem and not the Linksys' fault...
  8. Toastman

    Toastman Super Moderator Staff Member Member

    The technical aspects involved with transmitting data are what makes it necessary to use a wide bandwidth which happens to span over 4 of the old "channel numbers" that were used on this band. The assignment of the narrow "channel numbers" predates WiFi. Wifi is wideband, and a single wifi transmission uses several of those original channels. Unfortunately this does make referring to channel numbers very confusing. There are effectively only 3 WIFI channels in the band that don't interfere with each other, they are 1, 6 and 11 .

    You seem to have covered most everything. Oh - one last thing - don't forget the part that the wireless devices on the clients play in all this. It sounds like the wireless in your son's computers are a bit on the "crap" side. Many are. If they are USB adapters which are plugged into the back of the computer then try them on a USB extension cable to get them above the metalwork and in the clear - or even get them around the metal of the central heating. In apartment blocks, in rooms where signals are weak, a 5m extension to put the USB adapter next to the internal window or door works wonders.

    Apple devices tend to be very deaf (=CRAP), as do quite a few leading brands of Laptop/Netbook. I have several clients in rooms - where I get a very good signal from two or three AP's on my old Dell laptop - whose laptops can't even connect to one at all! Some of them now use a plug-in USB adapter and found it far better than the lousy wireless built into their laptops. (The TP-Link "G" USB adapters with an external antenna and higher power of 400mW are very good for this and are extremely reliable).

    Also, remember to turn off any power saving features that may be in the "advanced setup" of their wireless as that is usually responsible for dropped connections and poor speed.

    By the way, all of your neighbors signal are extremely weak, I wouldn't worry about them at all. Even -68 and -70 from your own routers is pretty weak, but quite acceptable.

    You may find increasing power to 150 makes things work better. Turn off APSD power saving mode, play with WMM and Interference Mitigation settings.
  9. garyfritz

    garyfritz Addicted to LI Member

    Both boys' computers use plug-in USB wifi dongles. Those always worked but unreliably. But something's changed now, and I can't connect to their wifi with my laptop, even sitting right next to it.

    Tried power=150, tried WMM on, no change. Couldn't find APSD or Interference Mitigation.

    Meanwhile the WAN port has started responding to pings for some reason, but I still can't connect to the management GUI from there.

    So... thanks VERY much for your patience and help, but I think it's time for a new router...
  10. Toastman

    Toastman Super Moderator Staff Member Member

    Or a priest :)

    No interference mitigation near to the WMM setting? Maybe you should try a newer build if you've been using that version for several years. Many bugs have been fixed since those days. Try 1.28.7628.1 which has some really nice new monitoring facilities :)

    You are trying to connect externally to the GUI with http://routerswanaddress:8080 ? DDNS problem?

    Good luck!
  11. garyfritz

    garyfritz Addicted to LI Member

    I just downloaded 1.28 yesterday, but it's 1.28.1816. Not a problem I hope?

    I don't see any interference mitigation. See attached.

    No, I use http://routerswanaddress -- actually just the IP address, I don't bother with the http:// -- always have, always worked before. Adding port 8080 doesn't help, but the router's not responding to pings now anyway... I connected to an internal port and the WAN address is what it should be, set to a static IP. It's just not responding to anything on the WAN port.

    When you suggested a priest I thought you meant an exorcism, but maybe you had last rites in mind... :D

    Attached Files:

  12. garyfritz

    garyfritz Addicted to LI Member

    FYI I grabbed an old DLink DIR615 off Craigslist for $20, and it's working like a charm. Should have done that long ago! Much stronger radio too, -25dB instead of -67dB. Strangely enough, the Netgear shows up as -47dB now, instead of the -70dB it showed before.

    So something was definitely wrong with the Linksys. No idea why the Netgear seems to have a stronger signal now but I'm not arguing!
  13. Toastman

    Toastman Super Moderator Staff Member Member

    There's something really strange going on there, - if you are now getting -25 and previously -67, then essentially the damned thing was acting as if it had no antennas on it :) And why should the Netgear read any differently when you only changed the Linksys? Remember that priest :)

    Glad you have something working now, anyway.
  14. garyfritz

    garyfritz Addicted to LI Member

    Huh. Just ran inSSIDer again -- and both the DLink and the Netgear are back at -70 or so. !?!?!??

    None of the neighbor SSIDs are visible now... whoops, one of them just popped up. It's almost like my laptop got better "hearing" after I installed the DLink, and now went back to "eh? what?" mode....

    Weird. Hopefully it will keep working and I can just ignore the damn thing...
  15. EOC_Jason

    EOC_Jason Networkin' Nut Member

    On my old WRT54GS v2 I have DD-WRT installed. The specific version is Eko VINT 15230... I don't know how much flash your model has, but you might want to give it a whirl. That version seemed to have the best wireless signal for me and has also been stable as a rock. Don't get me wrong, I love Tomato but it seems all the development is geared towards the newer routers that run the 2.6 kernel.


    Channel 14 is Japan only... Also it will only run at B speeds, NOT G (you can't force it)... If a setting isn't right then as you said it will fall back to channel 1. Wireless NICs can sometimes pick up channels above 11, from what I have read it depends on what SSID's they pick up first. So to avoid a bunch of headaches, just stick to between 1 and 11...

    As Toasman said, InSSIDer is an invaluable tool to figure out what wifi networks are around you and also how the signal is for your networks. Walk around your house (inside and out if you have a laptop) to see how the signals are. Walk the path between your router and to where the wireless computers are to see what signals are picked up. From there try to choose an open channel, or at least a channel with the minimal amount of other networks / signal strength.

    Try running just one router and doing your signal test, then plug in the second and see if things change. Make sure neither is set to "auto" for channel selection.

    Don't mess with the power settings... 9 times out of 10 they don't help and usually decrease performance (because it increases noise more than a usable signal). Set it back to default and reboot your router just to be safe.

    The location of your router can also make a huge difference. If it's on the floor then that's the worst... desk level is a little better... but if you can get it up high above all the usual clutter in a room then there's much less for the signal to have to go through.

    Why do you have two routers? Performance reasons? Content Filtering? Just because?
  16. garyfritz

    garyfritz Addicted to LI Member

    I have 3, actually. One "Gateway" router connects to the cable modem. The "Office" and "Kids" routers connect into Gateway. This provides isolation between the two networks to protect my business data from my kids' untidy web-browsing habits. It also lets me set the Kids router to automatically shut off their wifi at bedtime. :)
  17. xen0exe

    xen0exe Networkin' Nut Member

    Great advice.
    Turning off "interference mitigation" & "APSD" boosted my rate, speedtesting from 10 Mbps to 20+ Mbps from at least 3 rooms down.
    Im also on Channel 9, which I find most suitable for me, maybe because 1 & 11 each has at least 10 AP's.
    Will probably toggle with this setting for best setting, but so far setting above is awesome. It made me like router even more. :)
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