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why do OS/X apps fail when DNS is working fine?

723 Views 13 Replies Latest reply: Mar 24, 2014 2:45 AM by rAWTAZ RSS
random42 Calculating status...
Currently Being Moderated
Sep 5, 2013 2:12 PM

This is truely driving me nuts and based on the number of google hits I'm not alone.


Scenario: browser stops working

Go to shell:

$ ping - hangs

$ host - works fine

$ dig - works fine

$ dig -x IP - works fine

$ ping IP - works fine

$ ping - hangs


# killall -HUP mDNSResponder


makes no difference


# dnscacheutil -flushcache


makes no difference


Everything associated with DNS seems fine, so obviously OS/X apps don't use DNS directly...

what do they use ?


There must be a better way than rebooting the box every few days?

  • Baby Boomer (USofA) Level 9 Level 9 (55,540 points)
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    Sep 4, 2013 11:26 AM (in response to random42)

    When posting in Apple Communties/Forums/Message Boards.......It would help us to know which computer model you have, which OS & version you're using, how much RAM, etc. You can have this info displayed on the bottom of every post by completing your system profile and filling in the information asked for.




    CLICKY CLICK-----> Help us to help you on these forums




    ***This will help in providing you with the proper and/or correct solutions.***













  • Klaus1 Level 8 Level 8 (43,385 points)
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    Sep 4, 2013 4:33 PM (in response to random42)

    Scenario: browser stops working

    A description short of detail: what browser, and please define 'stops working'.


    Also, what apps (other than browsers) do you think should be using DNS?

  • BDAqua Level 10 Level 10 (114,745 points)
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    Sep 5, 2013 10:53 AM (in response to random42)

    How are you connecting & what are your DNS settings?


    What DNS settings are in your Router?


    Make a New Location, Using network locations in Mac OS X ...



    10.5, 10.6, 10.7 & 10.8…


    System Preferences>Network, top of window>Locations>Edit Locations, little plus icon, give it a name.



    10.5.x/10.6.x/10.7.x/10.8.x instructions...


    System Preferences>Network, click on the little gear at the bottom next to the + & - icons, (unlock lock first if locked), choose Set Service Order.


    The interface that connects to the Internet should be dragged to the top of the list.


    If using Wifi/Airport...


    Instead of joining your Network from the list, click the WiFi icon at the top, and click join other network. Fill in everything as needed.


    For 10.5/10.6/10.7/10.8, System Preferences>Network, unlock the lock if need be, highlight the Interface you use to connect to Internet, click on the advanced button, click on the DNS tab, click on the little plus icon, then add these numbers...



    (There may be better or faster DNS numbers in your area, but these should be a good test).

    Click OK.

  • MrHoffman Level 6 Level 6 (11,710 points)
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    Sep 5, 2013 11:14 AM (in response to BDAqua)

    As a guess, there's a bad DNS server in your ISP's DNS server pool.

  and are Google's open-access DNS servers.  Easier to remember than the ones BDAqua suggested, but the same request to try a different pool of DNS servers.


    FWIW, dig bypasses local DNS caching and goes to the default or the specified DNS servers, where ping uses local DNS caches

  • MrHoffman Level 6 Level 6 (11,710 points)
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    Sep 5, 2013 2:17 PM (in response to random42)

    Since this is a web browser that's involved and other services are apparently working, some other HTTP- or HTTPS-level component may well be in play here, such as a network filter, network security monitor, a firewall, or a network proxy server.   You'll have to check the local settings, and see where the "stops working" is arising.

  • BDAqua Level 10 Level 10 (114,745 points)
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    Sep 5, 2013 4:17 PM (in response to random42)

    So, is it using a Proxy Server in Sys Prefs>Sharing?

  • etresoft Level 7 Level 7 (23,900 points)
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    Sep 5, 2013 4:47 PM (in response to random42)

    random42 wrote:


    I'm sitting on a segment of a corporate network, DNS isn't the problem - it still works.

    Connectivity isn't the problem - it still works.

    The issue is that OS/X obviously uses something other than DNS to do name lookups - which doesn't always work, but no one seems to have a clue what that is.

    HUP'ing the usual suspects (mDNSResonder) and clearing caches makes no difference.

    Obviously DNS is the problem or else you wouldn't have posted anything. What happens when you use a 3rd party DNS like OpenDNS or Google? Does the problem go away? We are all using OS X too and not having any problems. Your problems must come from whatever is different about your network. Corporate networks often do funky things to network setttings and are rarely tested on anything but Windows. You seem pretty handy with UNIX, so use the scutil command to poke around at what your dynamic network configuration actually looks like.

  • g_wolfman Level 4 Level 4 (1,110 points)
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    Sep 5, 2013 5:09 PM (in response to random42)

    If a WINS server is pushing multiple search domains in the DHCP setup, OS X will not always pick them up and this can cause problems.


    scutil --dns will show you the current setup of the resolver cache, including the resolvers established for DHCP promulgated search domains.


    From Snow Leopard (or maybe Lion) onwards, all "native" DNS queries are made through the mDNSResponder Daemon, in much the same way that launchd acts as a "super-listener" for all active server ports coming inbound.


    If HUPing mDNSResponder is having no effect, then the daemon is working correctly, and it must be a problem in the configuration - again, something most likely caused by the DHCP setup when joining your network.

  • rAWTAZ Calculating status...
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    Mar 24, 2014 2:45 AM (in response to random42)

    random42: Have you found out any additional details on this matter?


    I've had the same thing happen a number of times, same symptoms although the problem is noticed when using Mail. I agree with what you say, it's like OS X's internal DNS infrastructure "hangs", even though DNS *is* fine - DNS lookups from the machine, using `host` etc, works fine. It's something inside OS X that stops working, and I haven't found a way to kick it live again either, nothing short of a reboot helps AFAIK at this point in time.


    It's been happening on both 10.8 and 10.9 for me. It might have been on 10.6 as well, I don't remember.


    EDIT: I'm gonna try the solution proposed in next time it happens.


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