Troubleshoot Wi-Fi issues in Apple Mac OS X Yosemite 10.10.4 with mDNSResponder

Apple Inc. recently tried fixing the year old Wi-Fi issue by releasing Mac OS X Yosemite 10.10.4 update, however, if you are still facing the problem then you can follow this quick fix whenever you land into such issues. It happens like this, you are connected to your Wi-Fi router, still the browser or any other Internet-based service fails to establish a connection, however, at the same time links work fine on the mobile or any other device.

There are two fixes for that:

The first way to do is the restart a service by “Force Quitting” it.

1.  Open the Activity Monitor from Launchpad > Other
2. Click on the Network tab in the corner.
3. Turn off your Wi-Fi and Router.
4. Look for something for mDNSResponder and select it.
5. Click on the little cross “x” above it and as shown in the picture below.
6. You will be asked: Are you sure you want to quit this process? With three options Cancel Quit and Force Quit. 
7. Click on Force Quit, Turn on your Wi-Fi and Router, you will be ready.

The second thing you can do is the remove the Bluetooth PAN from your network settings and everything will be good to go. To do that, you need to:

1.  Open System Preferences
2. Go to Network
3. Select your Bluetooth PAN
4. Click on the little ” – ” (Minus) switch and click on Apply.
5. Restart your router and Turn Off and On your Mac’s Wi-Fi.

Check the image below to know it more precisely.

The main reason behind the Yosemite to have such issues was the newly introduced process called as, DicoveryD, which soon was replaced by the old mDNSResponder. DiscoveryD didn’t perform well or may be it is still not that mature to handle the networking requests that easily.

First method will flush out the DNS Cache of the mDNSResponder which otherwise can also be done by using the Terminal.

1. Click on Launchpad
2. Open Terminal from from ‘Others’ folder
3. Enter this command [sourcecode language=”plain”]sudo killall -HUP mDNSResponder[/sourcecode]

   Hit Return.

The above command will restart the mDNSResponder process with HUP.

Comment if you have any queries regarding it.