When I run "networksetup -getdnsservers airport" in Terminal, it says There aren't any DNS Servers set on Wi-Fi
First run:

networksetup -listallhardwareports


Look for the en0 or en1 for your WiFi under the Device:

Then run:

ipconfig getpacket en0


Of course if your Wi-Fi is en7, then you need that instead of en0 above. The broadcast DNS and search suffix are provided as output to the above ifconfig getpacket command towards the bottom of the options. If you don't get a packed in response to DHCP then you need to fix that on your network or log in to the router directly to retrieve the proper values.