DNS issue

[#1]

Hi Guys

Has there been a problem with the default DNS servers over the past few weeks? I keep getting a DNS_PROBE_FINISHED_BAD_CONFIG error when trying to browse websites. The situation lasts from a few minutes to a few hours then spontaneously corrects itself. Rebooting the router has no effect.

Problem evident from 7:30 to 8:00 this morning and now evident since 10am.

Oh I have rebooted the router today and it has not fixed the issue.

Setting DNS servers to the Google ones on my laptop and everything works OK.

I can ping 212.159.6.9 and tracert with no issues but I still can't connect to any websites with the standard default route settings.

The DNS Settings on the router are all set to the usual default.

Any suggestions, please.

Kind regards

Kevin

[#2]

Hi Kevin.   I have been experiencing this same problem, for several months - interesting to learn that it's not just me. 

Plusnet Support initially suggested WiFi issues, which it clearly isn't.  Eventually they replaced my Hub One router but the problem persists. I am escalating.

I'll update the post when I learn more.

Craig 

[#3]

Thank you for your reply Craig.

It does seem to be an intermittent problem. When it is evident any device using the DNS settings on the router cannot access any websites. That's phones, tablet, TV's, NAS, laptops and desktops. If I change the DNS settings to use Google servers, they start working immediately, no need to reboot. Flushing and resetting the DNS cache has absolutely no effect.

Logic suggests it cannot be problem with the devices. It cannot be a Wi-Fi problem otherwise pinging the Plusnet servers would not work. Craig has a new router and the problem is still evident so it cannot be a router issue. I am using a Technicolor router so it cannot be a problem related to a specific type of router.

The error message suggests the DNS request from the browser has found no relevant entry in the database or the dns has simply not responded. I am suspecting the latter.

Plusnet's dns servers are not for public use. Surely Plusnet must check the request comes from a current Plusnet  customer. Anyone know how they do that? Does the dns check the request has come from a router with an external ip address that Plusnet has issued? If Plusnet are issuing external ip addresses to routers that the dns server knows nothing about then dns would not process a dns request from that external address I'm thinking. Hence the error message. It would only take a few "missing" ip addresses and the problem would not be evident, only to one of us lucky enough to get one. Of course rebooting the router probably means a new ip address and dns may know about that one so the issue appears to be fixed.

I'm logging the external ip address so I can see a pattern.

Not sure if this post is in the correct forum but Plusnet support did confirm they was no general issue related to this problem. They did suggest it may be related to the FTTP trial. Hence the post here.

Thoughts and suggestions gratefully received.

Kevin

[#4]

Kevin,

Interesting analysis. Your knowledge of DNS is greater than mine! 

It may help to add some more detail. I’m experiencing the following types of failure at different times when attempting to access web pages:

1. Long delay, then full web page is displayed (Browser status shows “Resolving host” for 5-10 seconds before displaying page.)
2. As (1) but renders page text only, no images etc.
3. Complete fail: Times out with DNS_PROBE_FINISHED_BAD_CONFIG
4. Fail then success: As (3) but after a further delay the full page is displayed (without any intervention from me).

I experience these with all devices, except strangely my Roku 2 has no problems accessing streaming services.

Incidentally I don't have Fibre to the Premises, just the standard fibre + copper service.

Question for you:  Changing DNS settings to use Google servers: is this an effective workaround?  If so how do I do this?

Cheers,

   Craig 

[#5]

Hi Craig

Thanks for your reply. It seems you have a slightly different issue to mine. Mine is either OK or I can't get any web pages to load if I am using the Plusnet DNS servers. Having reset my DNS cache and then rebooting the router, but making sure it was using a different external ip address seems to have solved my issue. Famous last words!

From what you say the about your issue, it would appear the DNS servers are having difficulty processing the request for that particular web page. I am assuming the problem is not related to any page in particular and you say more than one device is affected, apart from the Roku stick.

I would suggest you check you are using the DNS servers you should be first.

The Plusnet DNS Servers are 212.159.6.9 and 212.159.6.10 but some Routers are set to 212.159.13.49 and 212.159.13.50 it should not matter which you have.

Check on your router the DNS servers are set correctly on your Hub one router. Not sure exactly how you do that on your router. You may have to read the manual.

I think any Android device must use the router settings but with Windows PCs and Apple devices you can use DNS settings for that device. You are on your own with any Apple device.

For Windows you need to go to Change Adapter settings in the Network and Internet Settings (How you get there depends on the version of Windows). You need to select Properties (Give your password if a UAC box pops up). Then highlight Internet Protocol Version 4 (TCP/IPv4) and click on Properties. The DNS section is the lower half.

You should have Obtain DNS server address automatically selected. If so you are using the router settings.

You can change the DNS settings for that device while you are here and see how it goes. Check the Use the following DNS server addresses and set them to 8.8.8.8 and 8.8.8.4 respectively.

OK or close all the boxes and it may be a good idea to flush the DNS cache. Open a Command prompt with admin rights. (easiest way for Windows 10 , right click the start button and select Command Prompt (Admin))

First check the dns servers. Type ipconfig /all  you should see the DNS servers listed.

Then type ipconfig /flushdns and wait for confirmation.

Try using the google servers and see how you get on. Compare against devices still using the default ones on the router.

You may find your Roku device is using it's own dns settings, hence you don't have an issue with it. Not sure how to check the setting for that device.

If everything works OK then you can change back to using the router DNS settings. Otherwise if Google DNS are OK then change the router to use Google DNS. Just change the dns IP addresses on the router to those for Google.

Of course the PlusNet settings should be working OK so you may want to escalate the issue with Plusnet support if Google DNS works OK. If you decide to change things back make sure you go back to the initial settings you had.

Oh, I assume you are not using the Safeguard DNS server, both will be set to 213.120.234.42

Hope that helps

Kevin

[#6]

Hi Kevin,

Many thanks for the detailed, helpful reply. 

The DNS addresses on the router are 212.159.6.9&10. It seems these cannot be changed on my router model (Hub One).

I changed the settings on my Windows device to use Google and the DNS errors went away.  I haven't yet changed the settings on my Android phone, but mysteriously the problem has gone away on my phone anyway.   

I have escalated to Plusnet, since changing settings on devices is not a sustainable solution. I've suggested they fix the DNS service, or if they can't then replace my router with one which has user-settable DNS addresses.

Thanks again for your help.

Craig    

[#7]

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@ksjpope wrote:

Logic suggests it cannot be problem with the devices. It cannot be a Wi-Fi problem otherwise pinging the Plusnet servers would not work. Craig has a new router and the problem is still evident so it cannot be a router issue. I am using a Technicolor router so it cannot be a problem related to a specific type of router.

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Is this router a TG582n?

If it is you might find that disabling WanDownSpoofing protection eliminates the problem.

Some background to the effects of this is provided in post #103 of a huge topic https://community.plus.net/t5/Broadband/198-18-1-x-address-problems/m-p/1171271#M279937. along with the following instructions for disabling it:

(You can) turn OFF the Spoofing by telnetting into the TG582n and running the following commands.

dns server config WANDownSpoofing = disabled
dns server debug spoof clear
dns server debug spoof list
saveall
exit

The spoof 'clear' and 'list' commands are to make sure the list is empty (so your OS cache won't pick up any old spoofed addresses). (Try the spoof list command first if you want to see if there are any present.)

When you've done the above, then clear your OS (usually Windows) caches

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Sadly, for the Hub 1 I'm not aware of a similar "fix".