Database Users

VERY Strange WIFI problem

Ok
so for the last couple of days I've noticed that when at home, if I turn on the HD2's Wifi, my entire home network stops working. The router can no longer be accessed, even by wired Ethernet.
I figure it was a router issue, so I bought a newer better one by a different company - and what do you know: The same problem persists! As soon as I enable WiFi in my HD2 the router becomes unaccessible - and as I turn it off, all is well again.
I'm a computer technician, an MCSA and usually pretty good with those things, yet this issue baffles me. What on earth could cause that?
No other WIFI devices cause this issue, only my HD2.

Ambious said:
Ok
so for the last couple of days I've noticed that when at home, if I turn on the HD2's Wifi, my entire home network stops working. The router can no longer be accessed, even by wired Ethernet.
I figure it was a router issue, so I bought a newer better one by a different company - and what do you know: The same problem persists! As soon as I enable WiFi in my HD2 the router becomes unaccessible - and as I turn it off, all is well again.
I'm a computer technician, an MCSA and usually pretty good with those things, yet this issue baffles me. What on earth could cause that?
No other WIFI devices cause this issue, only my HD2.
Click to expand...
Click to collapse
What is the radio firmware version on the phone and what is the make, model and firmware revision of the router.
2 IT engineers are always better the one

My older router (with same problem) was 3Com 3CRWER200-75.
I replaced it with an Edimax BR-6524N. Same weird issue.
Both have latest firmwares.
My phone radio version... To be honst, I don't know how to check. My ROM version is 1.48.405.2 (71294) WWE - which is the stock rom of the Israeli version as supplied by Newpan.
Also worth mentioning, this didn't happen until a couple of days ago. Everyting was fine for months with the same exact configuration. SOMETHING must've changed, but what?
And how is it possible for my phone to kill two different routers?

I have the same problem with my laptop when running windows 7 but not linux....seems too me at least my problem is a driver issue.could be the damned for you too possibly. Was there a possible divert update on your phone?
I do not have an hd2 so I am not sure.
Edited for auto correct mistake

Ambious said:
My older router (with same problem) was 3Com 3CRWER200-75.
I replaced it with an Edimax BR-6524N. Same weird issue.
Both have latest firmwares.
My phone radio version... To be honst, I don't know how to check. My ROM version is 1.48.405.2 (71294) WWE - which is the stock rom of the Israeli version as supplied by Newpan.
Also worth mentioning, this didn't happen until a couple of days ago. Everyting was fine for months with the same exact configuration. SOMETHING must've changed, but what?
And how is it possible for my phone to kill two different routers?
Click to expand...
Click to collapse
You check your phone radio revision the same way you check your rom version. Go to settings, about phone, software information and look for the line "radio version".
Your actual rom version is quiet old and if you are still using a stock rom then you may want to have a look at the htc website for your country and see if you can get 1.66 rom or newer.
I personally have never experienced this problem but i always use linksys or netgear networking equipment. The linksys router i have at home i've had for many years (it's a wrt54g v2.0) and it still works perfectly even though it's cpu and networking chipsets are overclocked and it runs a custom firmware.

Well, the ROM is the latest available for my country :-(
But anyway, I managed to solve it by deleted all my wireless preferences and just 'rediscovering' my home network from scratch. Surprisingly that worked and solved the problem, even on my old router.
Now I'm wondering if I should return the new one and stick to my trust good old one, or stick with the new one? It was pretty expensive, and I don't really use an N wireless connection anywhere anyway, so... What do you think, XDA?

Ambious said:
Well, the ROM is the latest available for my country :-(
But anyway, I managed to solve it by deleted all my wireless preferences and just 'rediscovering' my home network from scratch. Surprisingly that worked and solved the problem, even on my old router.
Now I'm wondering if I should return the new one and stick to my trust good old one, or stick with the new one? It was pretty expensive, and I don't really use an N wireless connection anywhere anyway, so... What do you think, XDA?
Click to expand...
Click to collapse
You have no need for it, get your money back.

the hd2 is capable of N speeds. You just need to enable it in the registry. Personally i would use the old one till it dies and keep the newer one in a box till then but the choice is yours

The newer one is a lot of money I spent for something I didn't even need eventually. I'll be turning it back, I think.
Thanks to all who helped You guys rock!

Ambious said:
Well, the ROM is the latest available for my country :-(
But anyway, I managed to solve it by deleted all my wireless preferences and just 'rediscovering' my home network from scratch. Surprisingly that worked and solved the problem, even on my old router.
Click to expand...
Click to collapse
great to hear that you've found a solution!
A thought came to mind while reading this thread.
Wonder if it's possible that a certain radio file/setting on your HD2 might've been corrupted and instead of generating the usual wifi signal, it could've generated a signal on the same frequency that completely jammed you're router signal?
Similar to the radio jammer units available in some countries that can be used for GSM, Wifi, etc... just a thought!

Im glad you brought this up because I had the exact same problem (accept I could connect via ethernet just wifi went dead), almost brought a new router after spending 2 days trying to set it up :/ It wouldnt allow anything to see the router wifi wise let alone connect to it via wifi. I havent turned my wifi on the phone since then but ill try reseting my settings later to see if that works. I didnt wanna risk screwing the router over lol. Im on stock 1.48 rom and radio on o2 as well

bobbified said:
great to hear that you've found a solution!
A thought came to mind while reading this thread.
Wonder if it's possible that a certain radio file/setting on your HD2 might've been corrupted and instead of generating the usual wifi signal, it could've generated a signal on the same frequency that completely jammed you're router signal?
Similar to the radio jammer units available in some countries that can be used for GSM, Wifi, etc... just a thought!
Click to expand...
Click to collapse
That's an interesting thought, and if it's true - reversing it could be a tool for evil - just imagine being able to shut down networks just like that...
Anyway, I'm glad my issue was solved. That Edimax N router is really expensive, and I like my trusty old 3Com way better.

My N*kia n95 used to f*ck up the router like this sometimes

Legend wifi issues

Hi,
I am wondering if anybody has similar problems with wifi - 3g/data connection works perfectly, but when I am connected over wifi, after sometime the connection dies and I have to disable wifi and enable it again, in order to restore network access. I hoped that froyo would fix that, but as there is no froyo on the horizon I decided to ask.
The phone firmware is 2.1 update1
Software number 2.05.405.2
Sent from my HTC Legend using XDA App

Yes I get this too. The connection is still active but many apps suddenly decide to notify me that I need a WiFi/3G connection before I can use them. Turning WiFi off and back on fixes it. This also happens on my branded Desire running 2.1, which may imply it is related to the router settings. I will have to test on other routers. My WLAN is configured to 802.11g only, WPA2-PSK only (WPA-PSK and 802.11b not allowed) on channel 13.

actually great to know that i'm not the only one. i get this all the time, and i even emailed htc about this and response was retarded. they told me how to connect to my router. i tried pretty much everything on this issue. connect and reconnect, change channel from 13 to 11 or 14, nothing seems to be working. hopefully 2.2 will change all this.

evank418 said:
actually great to know that i'm not the only one. i get this all the time, and i even emailed htc about this and response was retarded. they told me how to connect to my router. i tried pretty much everything on this issue. connect and reconnect, change channel from 13 to 11 or 14, nothing seems to be working. hopefully 2.2 will change all this.
Click to expand...
Click to collapse
i think the htc legend has the worst wifi reception for all phones of 300 $
havent noticed a single improvement with every update

I had this problem with my first legend. The touch screen malfunctioned so I brought it back and got a replacement. The new one is much better. I am very happy with it.
For instance, in my home office I could never connect with my first legend, it would say association failed when trying to associate with the AP. On my new one it works and I've had it sitting on the desk now for about 4 hours and I picked it up and unlocked it and the wifi worked immediately.

I very occasionally had this until I switched the wifi sleep policy to never after reading somewhere that it would actually increase battery life and haven't had this problem since. Not noticed any difference with battery life though I only switch wifi on when I need it and off when I'm finished.
Sent from my HTC Legend using XDA App

For what it's worth, I have the same problem and I'm sure it's related to my phone, not the routers.
I hade no problems with this before my last OTA update...
Sent from my HTC Legend using XDA App

i dont want to hijack the thread but is the wifi antenna like **** for everyone or is just me?
im thinking that it might be the aluminium case that shield the antenna because reception is unbeliavable bad
im curious to know if desire/nexus mount the same wifi antenna as legend

if you put static ip it works perferct for me

shuikit said:
I very occasionally had this until I switched the wifi sleep policy to never after reading somewhere that it would actually increase battery life and haven't had this problem since.
Click to expand...
Click to collapse
where is this setting?

never had this problem...keeping an eye on this thread though just in case!

mtrax said:
where is this setting?
Click to expand...
Click to collapse
In wifi settings, press menu and then select advanced.
Sent from my HTC Legend using XDA App

I only have a problem very occasionally with wifi, maybe once per month, and I think this has more to do with my crappy router than anything else.

I have the same problem with WiFi cutting out afters while even when the phone hasn't been moved and when its situated inches from the router
Sent from my HTC Legend using XDA App

Generally it is not good idea to have router and client too close together. That way radio noise increases and that's not good.

Thanks for the tip. but it does it downstairs too when Im watching TV the phone is well away from all electrical appliances, after toggling wifi bOFF/ON I get full signal strength.

Same here. After a few minutes normal browsing on Wifi, pages seem get so far then refuse to load. Only solution is to turn WiFi off then re-connect. The WiFi permission is set to never sleep. I'm not rooted and running stock wwe 2.3 ruu.
Sent from my HTC Legend using XDA App

gazman69 said:
Same here. After a few minutes normal browsing on Wifi, pages seem get so far then refuse to load. Only solution is to turn WiFi off then re-connect. The WiFi permission is set to never sleep. I'm not rooted and running stock wwe 2.3 ruu.
Sent from my HTC Legend using XDA App
Click to expand...
Click to collapse
Same here!

Anybody have any ideas how to resolve this issue? It's really frustrating having to re-connect wifi every 5 mins. Possibly to do with debranding to stock wwe 2.3 ruu from Vodafone?
Sent from my HTC Legend using XDA App

having the same issue, despite having wifi on never sleep
looking forward to getting rid of this phone once I get my htc desire z, HTC doesn't seem to care about it since the only recent OTA they released made it worse

Wifi connected but doesnt work.

We have 3 SGS2 at home and a Billion 7800N modem
There is a recurring problem on my wifes phone where there is no dataflow. I cant even reach the modem. It will just start working all the sudden for a short period then stop again.
Things I have tried.
1. Using it right next to the router
2. have tried using different channel
3. have reset modem
4. made sure sleep policy is on never
5. Update firmware and hard reset phone - no new apps installed - worked at first but now having problems again.
It never loses wifi connectivity....internet just does not work. Turn 3g on...works fine.
What could be the problem?
Only things I can think of
1. Faulty phone
2. Virus? That phone is sometimes used to check out Chinese websites...and I know some of them can be dodgy. I forgot to ask her not to go to any of those sites after the hard reset as trial and error.
3. Not certain but this problem may only started when we updated to 2.3.4.
If need be Ill hard reset AGAIN when XXKG6 is out - I dont want to flash back to 2.3.3 to try

auswill2 said:
What could be the problem?
Click to expand...
Click to collapse
I have the impression, that the Broadcom WiFi drivers of Android are still buggy, because my Asus Transformer's WiFi also isn't very good.
When using a static IP address and setting Google's free DNS 8.8.8.8 as a secondary DNS server (the router as primary), my SGS2's WiFi works best.
Maybe give it a try.

I have the exact setup and tried all the things you mentioned to no avail. It works sporadically after I reset the phone wifi on and off but it won't maintain data connection for long. Although the signal indicator says it is still connected. the billion 7800 works on my wifes sgs and connects without problem to my work htc legend.
Sent from my GT-I9100 using XDA App

If you google for "galaxy s2 wifi no internet", you'll find out, that several SGS2 owners have exactly the same problem.
I all cases it seems to be the router's firmware, that causes this problem. I found two users reporting, that the only solution was to download a new firmware from ...
http://dd-wrt.com
But maybe it helps to drop the speed from 802.11 N to G?

I have the exact same problem and my firmwire on my router is the latest. What I do to fix this problem is just unplug my router and plug it back in. I find that fixes it for me. Post back if that doesn't work
Sent from my Nexus S using XDA App

isinisterx said:
... firmwire on my router is the latest.
Click to expand...
Click to collapse
That's why two guys reported, that they had to download a new FW from DD-WRT, which solved the problem for them.
Sorry, that I don't post links ... it were german forums.

I have the exact same problem. You say that the other two S2's work perfectly? If that's the case then it must be a hardware fault. I'm gonna take mine to be fixed or replaced.

steviewonders said:
If that's the case then it must be a hardware fault.
Click to expand...
Click to collapse
Likely ... maybe different firmware?

Yes....my SGS2 and my brothers work fine. When I update....I update all 3 so we are all using the same firmware.
Thats why I believe its a problem specific to 1 phone....not the router (although I did update my router to latest firmware just in case.....same problem)
As a side note - my brother has a microphone echo problem when using a specific gel case. When my wife and I use the exact same case - no problem. I dont know how Samsung build their phones - but its not very consistent.

auswill2 said:
Thats why I believe its a problem specific to 1 phone...
Click to expand...
Click to collapse
Shure ... in this case THIS phone has a hardware defect.
I dont know how Samsung build their phones - but its not very consistent.
Click to expand...
Click to collapse
That's why we have a thread about the "Made in ..."
But that's not only a Samsung problem ... I know that from the Asus Transformer forum.

Ill see where our phones are made if I have time. If anything though, my brother should be the odd 1 out as his was bought in Australia whereas I got the other 2 from UK.
Ill get to the bottom of this....even if I have to keep doing hard reset and trial and error tests. Not being able to use wifi is a huge deal.

Just to confirm, the problem's not only apparent in 2.3.4. My phone has the same problem with 2.3.3. I've sent my phone in for repair now so i'll post my findings here in a week or so. Have you got any further with it?

I sure hope they do fix it somehow....It's becoming increasingly annoying having to flick wifi on and off, downloading apps is the worst. This never happened on mine or my girlfriends htc's.

Anyone able to find a solution for this problem? Just picked up my Galaxy S2 and have the exact same issue Wifi connects, surf the net for about 10 sec, then nothing.. still connected to Wifi and everything.
At work at the moment so can't really play around with the router settings but will try once I get home. Have been looking forward to getting this phone for a while now and to have Wifi issues right off the bat is quite disappointing..

wifi connected no data flow
i had the same problem
i tried different ways no sucess
i tried Set DNS Pro from market
tried different settings
applied different dns
shift from open , custom to google ang keep checking the internet in browser
after few try it works everytime
its to do with assigning ip address in android
thanks

I posted a solution a few weeks back....but i think most people overlooked it....so the solution is
Go to settings>>>>wireless and networks>>>>>wifi settings>>>>hit menu and go to advanced>>>>regulatory domain>>>>change the channel to 14.....thts it....it worked for me on vibrant,nexus one and even on sgs2..hope this helps
Sent from my GT-I9100 using XDA App

zainqaiser said:
change the channel to 14
Click to expand...
Click to collapse
Channel 14 is not allowed in most countries ... my german router e.g. doesn't have channel 14, only 1-13.
I had similar issues with my Asus Transformer and found out, that a static IP works best, BUT only if a secondary DNS is assigned too. I used Google's 8.8.8.8
Give it a try. The Broadcom drivers seem to have a bug, when no secondary DNS is assigned.

The "regulatory domain" setting isn't there on my galaxy s2 ;/ Will give the static IP solution a try.

zainqaiser said:
I posted a solution a few weeks back....but i think most people overlooked it....so the solution is
Go to settings>>>>wireless and networks>>>>>wifi settings>>>>hit menu and go to advanced>>>>regulatory domain>>>>change the channel to 14.....thts it....it worked for me on vibrant,nexus one and even on sgs2..hope this helps
Sent from my GT-I9100 using XDA App
Click to expand...
Click to collapse
thx mate ..... this worked for me

I have the same problem currently on 2.3.4 (KH3) and I also had it on 2.3.3 (KF3).
I currently can't find the Regulatory Domain setting.

Wifi Signal Strength Issues

I've been looking everywhere for solutions to the weak Wifi on the Nexus 10, but didn't find any solutions yet.
The network also has an added wifi repeated connected via LAN, but still the Nexus keeps 1-3 bars of wifi.
I have another 5 or so Wifi devices, Galaxy S2, Lumia 920, iPhone, 2 laptops. None of these have any issues and are always on 4-5 bars, usually max all the time.
I've tested both on 2.4ghz and 5ghz, both to my Asus AC66U and also to an old RT-10, one Huawei, etc.
It's very clear that no matter the band or router settings, the Nexus 10 really has a weak signal reception in comparison.
Since the Nexus is new for me, it's on 4.3 and I don't know how it performed earlier.
Are there any other modem drivers or similar that can be flashed?
Any other experiences with custom ROM's?

Wifi strength has been a little weak since release honestly. Has been mentioned alot here and around the web for a while.
Now my problem since the latest update has been wifi drops where I lose wifi transfer completely even though the wifi icon shows a good connection.
I think this is something new (i know it is for me at least) and have been looking to see if anyone else has seen this issue in the latest software release.
If I toggle wifi off/on it works after but it is a huge pita.
Sent from my HTC EVO LTE using Tapatalk 4

tgrgrd00 said:
Wifi strength has been a little weak since release honestly. Has been mentioned alot here and around the web for a while. Now my problem since the latest update has been wifi drops where I lose wifi transfer completely even though the wifi icon shows a good connection. I think this is something new (i know it is for me at least) and have been looking to see if anyone else has seen this issue in the latest software release. If I toggle wifi off/on it works after but it is a huge pita.
Click to expand...
Click to collapse
This problem (wifi icon gray and no internet connection) started with 4.3 for me without question. Previously wifi connectivity was rock solid and I never gave a second thought to it. Nothing changed but the android version. I hope it is fixed in 4.4.

Ken401 said:
This problem (wifi icon gray and no internet connection) started with 4.3 for me without question. Previously wifi connectivity was rock solid and I never gave a second thought to it. Nothing changed but the android version. I hope it is fixed in 4.4.
Click to expand...
Click to collapse
Yeah, another guy at work told me his is doing the same after 4.3. Surprised we aren't seeing it mentioned more around here.
Anyone else seeing wifi drops?
Sent from my HTC EVO LTE using Tapatalk 4

tgrgrd00 said:
Yeah, another guy at work told me his is doing the same after 4.3. Surprised we aren't seeing it mentioned more around here.
Anyone else seeing wifi drops?
Sent from my HTC EVO LTE using Tapatalk 4
Click to expand...
Click to collapse
mine was doing the same thing. i tried clearing the cache, uninstalling apps that i thought might interfere and then a full factory reset. still had the same problem. i rooted and then did a factory reset from recovery and it hung up reinstalling apps so i did another factory reset still in and out. i did another factory reset and logged into my wifi and left for a few hours to work on something else. when i got back the signal showed full and about half of the apps installed. i reinstalled all of the apps that hadn't installed and it's working fine now. not sure why i had to wipe it 4 times but it's working fine now and streaming movies without a hiccup. i guess something kept getting corrupted during the setup or reinstall of apps. anyway it's been working fine for a few hours which is the best it's done in the last month.

Wi-Fi Channels 12/13

Anyone having issues connecting to wi-fi networks on channels 12/13? On my device I'm unable to see SSIDs in these channels most of the time. Sometimes I can see networks in channel 13.
Am engaging with Google tech support, so will keep you posted.

What country are you in?

UK

I seem to be the only person on my street that knows channel 13 exists. No issues for me connecting. Although I run my phone to my 5Ghz connection normally, I can connect to my 2.4Ghz if needs be.

TheReverend210 said:
I seem to be the only person on my street that knows channel 13 exists. No issues for me connecting. Although I run my phone to my 5Ghz connection normally, I can connect to my 2.4Ghz if needs be.
Click to expand...
Click to collapse
Good good.
I'm wondering whether it's down to me not activating the SIM in the phone as yet? Like a double check that the phone should be allowed to use 12&13 (rather than just selecting English UK as the language).

TheReverend210 said:
I seem to be the only person on my street that knows channel 13 exists. No issues for me connecting. Although I run my phone to my 5Ghz connection normally, I can connect to my 2.4Ghz if needs be.
Click to expand...
Click to collapse
There's really no difference in using that over channel 11 in your case with the co-channel interference.

YES!
It's not just me then. Home router (2.4Ghz) is on ch.13 and when i return home the device will not auto-connect until i toggle wifi off and back on again. Wifi works fine until i leave again. connects fine to my wifi network at work but that is different channel and on 5Ghz too.
RMA'd my device and the new one was bad. Wouldn't see my network at all, but wouldn't register my Sim card either so I have just returned this replacement device. Replacement number 2 is on the way.
I switched to ch.12 and the same thing happens at home. Didn't try any other channels as they are too noisy. So I wonder if this is a software issue? I'm in the UK and the router is made by technicolor for Plusnet.

j3di said:
YES!
It's not just me then. Home router (2.4Ghz) is on ch.13 and when i return home the device will not auto-connect until i toggle wifi off and back on again. Wifi works fine until i leave again. connects fine to my wifi network at work but that is different channel and on 5Ghz too.
RMA'd my device and the new one was bad. Wouldn't see my network at all, but wouldn't register my Sim card either so I have just returned this replacement device. Replacement number 2 is on the way.
I switched to ch.12 and the same thing happens at home. Didn't try any other channels as they are too noisy. So I wonder if this is a software issue? I'm in the UK and the router is made by technicolor for Plusnet.
Click to expand...
Click to collapse
If channel 11 is noisy, then so is 12 and 13.
Sent from my Nexus 6P using Tapatalk

TheReverend210 said:
I seem to be the only person on my street that knows channel 13 exists. No issues for me connecting. Although I run my phone to my 5Ghz connection normally, I can connect to my 2.4Ghz if needs be.
Click to expand...
Click to collapse
You might want to change to channel 11. With the current setup you are not only killing your own data rates, but also the rates of everyone on channel 11. These channels are not supposed to overlap, because that creates interference. Switch to channel 11.

This is my WiFi situation. I'm normally on CH.13, but switched to 12 as a test.

My 2nd unit arrived last week, and unfortunately it's the same issue as before - no channels 12 or 13, not even visible. I'll be back in touch with Google today.
Hopefully this is a software issue rather than Google/Huawei spec'ing a duff wifi chipset.

Google spoken to and basically it's a case of tough-titty - some devices aren't going to work with channels 12 & 13.

For anyone else reading this, I had this problem and 'solved' it.
If you find that you can't see channels 12 and 13 then it's almost definitely caused by the Wifi country code restrictions.
I got my Nexus 6P here in Korea and initially tried it out with no sim card. Even though the location is set in settings, without a sim card it doesn't get the wifi country code set, and I couldn't see those channels. As soon as I inserted a Korean sim card, I was able to see them.
If you are in the UK or elsewhere, using a local sim card and you can't see those channels then chances are either your country doesn't allow it or the code is already set. Either way, your options are just accept it or try one of the 'not officially supported' ways to getting around it. That's likely why Google said you were out of luck. It's possible but involves rooting etc. I think. Just search for 'change wifi country code android'. Good luck.

throwawaynexus said:
For anyone else reading this, I had this problem and 'solved' it.
If you find that you can't see channels 12 and 13 then it's almost definitely caused by the Wifi country code restrictions.
I got my Nexus 6P here in Korea and initially tried it out with no sim card. Even though the location is set in settings, without a sim card it doesn't get the wifi country code set, and I couldn't see those channels. As soon as I inserted a Korean sim card, I was able to see them.
If you are in the UK or elsewhere, using a local sim card and you can't see those channels then chances are either your country doesn't allow it or the code is already set. Either way, your options are just accept it or try one of the 'not officially supported' ways to getting around it. That's likely why Google said you were out of luck. It's possible but involves rooting etc. I think. Just search for 'change wifi country code android'. Good luck.
Click to expand...
Click to collapse
I am afraid that the issue is not as simple. I also have problems with channels 12 and 13, however my phone can connect to those channels, but only for a while. I quote the report I filed in the AOSP bug tracker (not yet assigned, though):
Before I continue, I am based in Switzerland, use a Swiss mobile provider (Swisscom), and I bought my phone through Google in Switzerland. This is relevant because in Europe 802.11b/g/n channels 12 & 13 are allowed, while in the North America they are allowed only under "low power conditions" with the effect that, AFAIK, many devices simply do not support them. My Nexus 6P however should (and shall) support those two channels.
Now, the problem.
I have two access points at home, both in the 2.4 GHz band: one on channels 4+6 and the other (normally) on channels 12+13. What I noticed is that my Nexus 6P would initially connect to the strongest signal independently from the channel, as expected, but then after a while (a couple of hours, maybe) would just stop seeing the signal on channels 12 & 13. Not just my own WLAN, but also neighborhood WLANs on the same channels. This means that the phone can be sitting a couple of meters from the AP in my office (channels 12+13) and be connected to the AP at the opposite corner of the building (the one on channels 4+6). I checked with "WiFi Analyzer" and the phone really does not see any signal above channel 11.
Disabling and re-enabling WiFi will make the phone see channels 12 & 13 once again. However after a while the problem appears again.
At home this is just an inconvenience: I moved the frequency of the second AP to a different channel and that "solved" the problem. On the other hand this might be a much more serious problem when I am in an environment where I can't change the WiFi settings. Maybe I want to connect to a public hotspot broadcasting on the "wrong" channels or I am at the office in an area covered by APs on channels 12 & 13. Tough luck.
Incidentally, I saw at least one report of someone who had exactly the same issue: he had to disable WiFi and enable it again to get the phone to connect to his WLAN (on channel 12 or 13, I can't remember). I also have to say that in our household we have a few other Android devices (2 x Nexus 7, 1 x Nexus 9, 2 x Nexus 4, 1 x Moto X Play) running either 6.0.1 or 5.1.1 and a few other devices (iPhone 5S, iPhone 6, laptop, 2 x Kindle) and none exhibits this behavior. It seems to be specific to the 6P.
I suspect that after a while the WiFi driver simply reverts to its default regulatory domain ("US", I assume) and stops listening to channels 12 and 13. Why it might do so is anyone's guess. Maybe doze interferes with the driver.

Same problem here. The only way to reconnect to WiFi channel 12 or 13 is to manually switch WiFi off and on again on the 6p.
I'm in Hungary.

Guys, there is a thread in the Nexus Help Forum and I reported the issue in the AOSP Bug Tracker. Add your contributions to those threads and star them. Let's try to bring this to Google's attention, otherwise we will never get any action on this topic.
Edit: For some reason I can't add links to the post. Please search issue 197106 ("WiFi 2.4 GHz channels 12 & 13 not working properly on Nexus 6P running 6.0.1") in the AOSP Bug Tracker and the post "My Nexus 6P can't connect to Channel 12 or 13 WIFI's" in the Google Product Forums.
Roberto

I have been trying for a week to extract some information from Google and Huawei, but I must say that their support just doesn't know anything about this issue. It's even difficult to get someone to understand what the problem is: one Google support guy thought I was talkng about LTE channel 12, for example. Huawei support started talking about options in the WiFi settings that are not there, then they wanted to guide me through adding a new WLAN, and finally started clutching at straws, giving more and more fantastic explanations of why it might be so.
Bottom line is: nobody I talked to ever heard about this issue.
I would really like to understand if it could be a hardware issue (which I honestly doubt) because my RMA window is closing soon and I don't honestly know what to do: apart from this WiFi issue my 6P is absolutely flawless and I do not want to risk getting a new telephone only to find out that WiFi still does not work as expected and it's also got other issues. (And, yes, something like this already happened to me.)

robertototaro said:
I have been trying for a week to extract some information from Google and Huawei, but I must say that their support just doesn't know anything about this issue. It's even difficult to get someone to understand what the problem is: one Google support guy thought I was talkng about LTE channel 12, for example. Huawei support started talking about options in the WiFi settings that are not there, then they wanted to guide me through adding a new WLAN, and finally started clutching at straws, giving more and more fantastic explanations of why it might be so.
Bottom line is: nobody I talked to ever heard about this issue.
I would really like to understand if it could be a hardware issue (which I honestly doubt) because my RMA window is closing soon and I don't honestly know what to do: apart from this WiFi issue my 6P is absolutely flawless and I do not want to risk getting a new telephone only to find out that WiFi still does not work as expected and it's also got other issues. (And, yes, something like this already happened to me.)
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Hello, I also have the same problem. As I can report it to Google? I have not found a way.

gmarti said:
Hello, I also have the same problem. As I can report it to Google? I have not found a way.
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Did you call the Google Store Support? I hope that if they hear the same reports repeatedly they will take notice.

If your telephone is unlocked (and if you are on XDA chances are it is), flash Franco's kernel. I did it today and now my problems with WiFi are gone. Plus Franco's is known to be very battery efficient. It's a win-win situation.