Andy987
Level 1 (0 points)

Q: DNS not working after waking iMac

Since installing 10.10.3 on my early 2009 iMac (hardwired, not WiFi) I've had an extremely annoying issue where my iMac will not see anything on the internet for nearly 2 mins after waking up. It's actually quicker for me to re-boot in order to regain internet connectivity.

 

I'm fairly certain it's a DNS problem. Every time this happens there's a message like:

 

09/05/2015 08:56:40.637 configd[51]: [0x7fb4da47e510] [m]DNS query timeout (query time = 2665.080478), [TE]

 

in the console about 30-40s after waking. But I'm not seeing anything else obvious.

 

Is anyone else anything seeing anything like this?

 

The problem is not the network itself - during the 2 mins of internet "silence" I can still connect to anything on my LAN without a problem using Bonjour name resolution or IP addresses. It's only WAN network operations that require a full DNS lookup that cause a problem.

 

I think the LAN itself if fine - it's only this iMac that has this problem (multiple other devices are fine). As above the iMac is hardwired, to an Airport extreme.

 

I've tried:

  • Changing my DNS servers to/from the Google servers in the router
  • Manually configuring them on the iMac rather than relying on DHCP
  • Using WiFi rather than hardwire
  • Deleting most relevant files in /Library/Preferences/SystemConfiguration/ (e.g. Preferences.plist)

 

And have now run out of ideas. Any further suggestions gratefully received.

Posted on May 9, 2015 1:34 AM

by Andy987,Solvedanswer
Andy987 Andy987
Level 1 (0 points)
A:

Am posting this in case it helps someone else.

 

As I suspected this looks like a problem called by the new discoveryd daemon which replaced mDNSResponder in Yosemite. Search for discoveryd and you'll see all the problems people have been having with it. Anyway I tried a solution which someone claimed to have worked for them and it looks like it's worked for me too:

  • Turnoff all Apple TVs you have on your network
  • Reboot any Airport Express, Airport Extreme or Time Capsule you have on your network
  • Turn your Apple TVs back on

 

Haven't had a problem in days since doing this. Hope it works for you tool.

Posted on May 14, 2015 11:53 AM

Close
Andy987

Q: DNS not working after waking iMac

  • All replies
  • Helpful answers

  • by cdhw,Helpful

    cdhw cdhw May 9, 2015 5:58 AM in response to Andy987
    Level 4 (2,653 points)
    Servers Enterprise
    May 9, 2015 5:58 AM in response to Andy987

    I think that the answer will be in your system log, which you can inspect with Console.app.

     

    You haven't mentioned checking that your hosts file:

     

         /private/etc/hosts

     

    hasn't been messed with. It's a bit of a long shot, but maybe you have unintentionally installed some adware/malware that is messing around. Use EtreCheck:

     

         http://www.etresoft.com/etrecheck

     

    and post the results here if you are not sure what you are looking for.

     

    C.

  • by Andy987,

    Andy987 Andy987 May 9, 2015 6:26 AM in response to cdhw
    Level 1 (0 points)
    May 9, 2015 6:26 AM in response to cdhw

    Thanks for the good suggestions - they helped to eliminate some other potential issues but unfortunately neither yielded any answers:

    • My hosts file looks exactly as I'd expect
    • Etrecheck didn't show anything unexpected, although it reminded me I had LittleSnitch installed (since uninstalled/retested to no avail).

     

    The message I quoted was actually from my System Log and was the only thing that looked abnormal to me. In case it helps it's definitely happening as an OS level (e.g. not Safari). For example, this is what I get from a command line during first minute or two:

    iMac:~ Andy$ ping www.google.com

    ping: cannot resolve www.google.com: Unknown host

     

    And then a minute later:

    iMac:~ Andy$ ping www.google.com

    PING www.google.com (216.58.209.228): 56 data bytes

    64 bytes from 216.58.209.228: icmp_seq=0 ttl=58 time=7.574 ms

     

    Personally I suspect this is yet another discoveryd issue as I've had no end of network issues with Yosemite.

  • by Andy987,

    Andy987 Andy987 May 10, 2015 12:10 AM in response to Linc Davis
    Level 1 (0 points)
    May 10, 2015 12:10 AM in response to Linc Davis

    Thanks but I don't think it's a problem with the DNS servers themselves. As above, only the one iMac is impacted.

  • by Andy987,Solvedanswer

    Andy987 Andy987 May 14, 2015 11:53 AM in response to Andy987
    Level 1 (0 points)
    May 14, 2015 11:53 AM in response to Andy987

    Am posting this in case it helps someone else.

     

    As I suspected this looks like a problem called by the new discoveryd daemon which replaced mDNSResponder in Yosemite. Search for discoveryd and you'll see all the problems people have been having with it. Anyway I tried a solution which someone claimed to have worked for them and it looks like it's worked for me too:

    • Turnoff all Apple TVs you have on your network
    • Reboot any Airport Express, Airport Extreme or Time Capsule you have on your network
    • Turn your Apple TVs back on

     

    Haven't had a problem in days since doing this. Hope it works for you tool.