Automatically assign DNS

How do I ensure that the DNS is being set by the network?

On Windows I would check here and make sure that Obtain DNS server address automatically was selected:

DNS


Open System Preferences and click the Network icon.

Screen shot of System Preferences

Select your network in the list on the left, and make sure that it says "Using DHCP" in the drop-down list after "Configure IPv4:"

Screen shot of Network Settings

If you've made any changes, click the "Apply" button and then the "Show All" button to make sure everything is saved.