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Thread: very very odd network problem

  1. #1

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    l33t! MrPolite's Avatar
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    very very odd network problem

    I'm PUZZLED, read below please
    -every now and then IE and Firefox are unable to browse websites (as though there is no connection... loading any website will immediately fail)
    -When this happens, other internet-bound programs continue to work fine (i listen to live stream of music, and i continue to chat online)
    -Pinging certain popular websites like yahoo and google fails (cannot find host), while certain websites that I have visited recently ping fine.
    -While pinging yahoo.com on my computer fails, I tried to use the router ping utility and it seemed to work fine
    -so far i have only noticed this problem with the HTTP protocol
    -the problem usually goes away within a minute.... sometimes happens again within 5 minutes!


    -I'm on wireless G, using a Linksys WRT54G router.
    -I'm thinking this can't be a wireless interference, because otherwise other applications would fail as well
    -I was also thinking that the router might be messing up with it's DNS cache, but that couldn't be the case either, because the router's ping tool works and windows ping on my computer doesn't work for certain websites


    ANY ideas?
    Last edited by MrPolite; Jan 29th, 2008 at 11:48 PM.
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  2. #2
    Super Moderator si_the_geek's Avatar
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    Re: very very odd network problem

    When it happens, can you ping those sites (or connect to them) via the IP address?

    If you can, then it would seem to be a DNS issue (I presume your router has it's own DNS cache).

  3. #3

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    Re: very very odd network problem

    hmm brilliant... i only could test it once
    but if i did it right, it's the DNS that cannot be resolved
    but why ?
    the router's ping utility works fine, so on the router's end the DNS cache should be working fine
    why wouldnt the DNS map correctly when I'm on my computer?!!!
    i cant think of any reason why the local dns cache would become invalid periodically

    edit: problem persists with wired connection on this same computer
    Last edited by MrPolite; Jan 31st, 2008 at 12:03 AM.
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  4. #4
    Super Moderator si_the_geek's Avatar
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    Re: very very odd network problem

    Many routers have a DNS cache, and presumably keep it full even if they cannot reach a DNS server to verify that it is still valid.

    I'm not sure how/where to check, but it is possible that your computer is set to not keep a cache, and therefore requires an active DNS server.

    Assuming that both of the above are true in your case, I would think that the DNS server is refusing to reply to you at that time. I'm not an expert on this, so hopefully somebody with more knowledge will reply soon.

  5. #5
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    Re: very very odd network problem

    What are you using for DNS on your computer? Your router's address or your provider's DNS server's address? The router can use either, but if the computer is pointed at your provider's server, it won't use the router if the provider's server fails temporarily.
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  6. #6
    PowerPoster stanav's Avatar
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    Re: very very odd network problem

    Cox is my ISP and their DNS servers suck... Every once in a while, those servers are down for no reason. So I decided to try those public DNS servers, and to my supprise, they are much faster and more reliable than my IPS's. My favorite ones are from OpenDNS:
    208.67.222.222
    208.67.220.220
    You can Google for free public dns and theere are tons of them out there to pick from if you're not happy with the dns servers your isp provides.

  7. #7
    VBA Nutter visualAd's Avatar
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    Re: very very odd network problem

    DNS uses UDP, which when there are communication problems is more likely to fail. You are likely to expecrience a slow than usualy resolution before it fails completely; but instant failure is more unusual.

    Some home routers do however have a tendancy to fire their own address back when a DNS lookup fails. Windows does have a DNS cahce and it cna be flushed using: ipconfig /flushdns.

  8. #8
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    Re: very very odd network problem

    Quote Originally Posted by MrPolite
    -While pinging yahoo.com on my computer fails, I tried to use the router ping utility and it seemed to work fine
    Disable your firewall and enable DMZ. DMZ settings will be in your router, this will leave your pc vulnerable to hackers, so dont use it as a permament solution if it works.

    If its only started happening recently try system restore.
    If your question is answered then mark your thread RESOLVED and give credit to whoever answered it.

    If you fail, try and try again, its the only way to success.

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