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I am having an interesting problem at home that I have not seems before. I was visiting a few sites and noticed that their DNS was not resolving. They are big sites so I knew that they couldn't be down or something silly like that. I did some googling and found that this can sometimes happen with your ISP and so I plugged in google's DNS servers to use. This fixed some of the problems but other sites were still not resolving.

I then switched back to 'dynamic' mode and let Windows select the best DNS servers but then I also added Google's servers to be used as a backup. So far so good I haven't had any issues yet but it seems like some of the sites are taking a slightly longer time to load (probably because it has to cycle through the DNS servers provided in order to find one that works).

Is this common? Should I be worried about a virus? Could this simply be an ISP only issue?

thanks,

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  • Doesn't sound fishy to me, sounds like the normal pains of DNS but you've tackled it well and assumed correctly about the long loading times
    – codaamok
    Oct 4, 2016 at 13:45
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    The "backup DNS servers" don't work like you think they do. If the first one answers (including an answer of 'I have no idea what google.com is') then the secondary isn't checked. The secondary is only used if the primary doesn't answer at all. Perhaps see this SU question: Alternate DNS server not resolving after first one fails to resolve Oct 4, 2016 at 13:53
  • Yes I know that, I just mean for sites that do hit that third or forth DNS server its going to take longer to resolve that site than a site that resolves from the first DNS used. Oct 4, 2016 at 13:54
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    You say you know that, but what you're saying seems to conflict with it. :) If the first DNS server answers (even with "unknown"), then the secondary+ DNS servers are not checked. The only way you'll ever request addresses from the secondary DNS server is if the primary is offline. Your computer uses DNS to find IPs, not the "sites". So regardless of the site you're trying to hit, you're always using your chosen DNS servers, in the order your computer is set to use them. Hope that helps clarify, in a way that will help you track you problem down. :) Oct 4, 2016 at 14:00

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Sometimes sites can just be slow (overloaded webserver, bad downstream connection, network issues), rarely it is DNS related, DNS should resolve instantly and once a site has been opened once, the DNS is almost always cached in your system. So loading the same site in a row should already be enough to exclude a DNS related problem.

General slowdown when having issues in page loading I would suggest making sure that you do not have any unnecessary plugins in your browser, try opening an "in cognito / private " (this usually disables plugins) browser window and see if the speed improves.

If you initially had DNS problems I can recommend the google DNS servers over your provider's as a rule of thumb, I control numerous servers and remote computers, they all use google DNS as the default configuration and I've never had issues related to them (provider DNS is another story).

If you wish to dig deeper in the subject, you could open a cmd window (windows key + R , type cmd, press enter) and run an "nslookup" command, for example 'nslookup amazon.com' should tell you the IP adres behind the website and give you an idea how fast they get those results.

If you wish to determine why a website is running slowly you could run the (in chrome/firefox) network tab m in chrome this is accessed by pressing F12 and clicking the Network tab, then refreshing the page, this should reveal exactly what is slowing up the page loading and find potential issues.

example result of the network tab: https://developers.google.com/web/tools/chrome-devtools/network-performance/imgs/network-panel.png (this site displayed there loads completely in under a second, which I would say is a fairly good result)

All of this expecting that your own connection is good, be sure to test it on a computer that has wired connection, wifi in general is the cause for many reliability issues in general connection stability.

Sorry for the long message, hope it helps :)

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