From another post I read this:
I want to use the internet optimizer.
But I got the return message "Error: Internet Optimizer cannot be run on this system because you are using a local network based DNS."
What's meaning? Does it mappen when I use to connect the internet by a WLAN?
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The error message means your internet connection is using a local network based DNS. For example, this the DNS setting of your computer has been set to point to your router box and your router uses some external DNS to do the actual domain name service. In these cases, you should configure your router first in order to be able to use custom DNS server.
How do I do that at my router 'tp-link Archer C6 v2.0'
Regards Jonny