On Mac OS X
How to change the DNS server settings on a Mac PC.
Example: Changing DNS server settings on Mac OS 10.5
From the Apple menu, click System Preferences as below:
Then click Network as highlighted with the arrow:
If the lock icon in the lower left-hand corner of the window (highlighted in below screenshot) is locked, click the icon to make changes, and when prompted to authenticate, enter your password.
Select the connection for which you want to configure Google Public DNS.
For example:
To change the settings for an Ethernet connection, select Ethernet/Built-In Ethernet, and click Advanced.
To change the settings for a wireless connection, select Wi-Fi/Airport, and click Advanced. (As shown below)
Select the DNS tab as below:
Click + to replace any listed addresses with, or add, the Google IP addresses at the top of the list as shown below:
For IPv4 Select: 8.8.8.8 and/or 8.8.4.4.
Click Apply and OK.
To Test that the Google DNS Resolver is Working:
Step 1 - From your browser, type in a hostname (such as http://www.google.com/ ). If it resolves correctly, bookmark the page, and try accessing the page from the bookmark. If both of these tests work, everything is working correctly. If not, go to step 2 below:
Step 2 - From your browser, type in a fixed IP address. You can use http://18.62.0.96/ (which points to the websitehttp://www.eecs.mit.edu/ ) as the URL.* If this works correctly, bookmark the page, and try accessing the page from the bookmark. If these tests work (but step 1 fails), then there is a problem with your DNS configuration; check the steps above to make sure you have configured everything correctly. If these tests do not work, go to step 3 below:
Step 3 - Roll back the DNS changes you made and run the tests again. If the tests still do not work, then there is a problem with your network settings; contact your ISP or network administrator for assistance.
Repeat the procedure for additional network connections you want to change.