Apple – iOS 7
Here we show you where you can edit the DNS for a WIFI connection. 3G or LTE connections cannot be changed, because the traffic is transmitted via the cell phone network and is terminated by your cell phone provider in their internet network. You also have to change the DNS for every WIFI network you use. You just have to do it once. If your iPhone connects again to this network the previously saved DNS settings will be used.
Open the System Preferences and tap the Preference Icon on your home screen
2. Select WIFI Network
Tap on the line of the WIFI Network to see all your WIFI networks and the current one.
3. Edit the WIFI Network
Tap on the “i” on the right side of your network.
4. Enter the IP-address
You see now all details and a line labeled with DNS. Tap directly on the number you see and you can enter a new IP address.