Monday, May 31, 2010

mDNSResponder Constantly Doing "Something"

I noticed my mDNSResponder connecting constantly to opendns (didn't always happen but when it did it was constant). Found the links below. It basically requires a bit of under-the-hood tweaking.

  1. Make a back up copy of the mDNSResponder.plist file as a precaution.
  2. Open the mDNSResponder.plist file in Terminal using your preferred text editor. Here is a sample command:
    sudo nano "/System/Library/LaunchDaemons/" 
  3. Add "<string>-NoMulticastAdvertisements</string>" to the array in the "ProgramArguments" section.

    In other words:
    <string>-NoMulticastAdvertisements</string> </array>
  1. Save the file.

    : If you edited the file using emacs, you must remove the emacs backup file (the file with a tilde at the end of the name, "/System/Library/LaunchDaemons/") or your Mac will not start up.
  2. Restart your Mac.


UPDATE 12 June 2010: The problem, as it turns out, was listing my OpenDNS servers in both my Airport Extreme (for the entire home network) and my Mac Pro. As soon as I deleted the OpenDNS servers from Network Preferences on my Mac Pro, everything returned to more constant outgoing connections. The above method worked too, but it was at the cost of losing Bonjour connectivity on my home network (not acceptable).

[From Snow Leopard disabling mDNSResponder/Bonjour drops internet - Mac Forums]

Mac OS X v10.6 uses the mDNSResponder process for unicast DNS (Domain Name System) functions, as well as Bonjour functions. Disabling the mDNSResponder process will also disable unicast DNS resolution, and without unicast DNS resolution, Mac OS X v10.6 cannot resolve hostnames such as

In some network environments, administrators may prefer that Mac OS X v10.6 not transmit Bonjour service advertisements. You can use this advanced article if you are a network administrator who needs to disable Bonjour advertising service without disabling Bonjour queries and DNS.

[From Mac OS X v10.6: Disabling mDNSResponder will disable DNS]

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