Changing the DNS server: when, where and the risks

What the message looks like

Webseiten laden nicht, obwohl das WLAN verbunden ist; ping 8.8.8.8 geht, aber nslookup example.com scheitert.

Common causes

• The provider's DNS server or the router's DNS service is faulty or overloaded.
• A wrong or outdated DNS entry is set in the router or on your computer.
• A filter or ad blocker in the network blocks the name you want to open.
• A cached (old) entry returns a wrong address.

Check

1. Does a plain address work? If yes, DNS is the likely cause (Windows: ping -n 4 …)
   ping -c 4 8.8.8.8Copy
2. Does the router's DNS answer?
   nslookup example.comCopy
3. Does another DNS server (Google 8.8.8.8) answer?
   nslookup example.com 8.8.8.8Copy
4. Windows: clear the DNS cache
   ipconfig /flushdnsCopy

Fix

• Run the tests above. If nslookup example.com 8.8.8.8 works but nslookup example.com does not, your current DNS server is the problem.
• The best place to change it is the router: in its menu under home network or internet, enter the DNS server, and it applies to every device. Alternatively change it on a single PC in the network settings.
• Well-known public DNS servers are Cloudflare 1.1.1.1, Google 8.8.8.8 and Quad9 9.9.9.9. Enter one as preferred and a second as alternate.
• Mind your privacy: the DNS provider you pick can see which names you look up. Read its privacy policy and decide on purpose.
• Then clear the cache (ipconfig /flushdns on Windows) and verify with nslookup example.com.
• If all works again, you may report the fault to your provider or keep the new DNS server.

FAQ

Is a public DNS server faster or safer?

Not automatically. Sometimes it answers faster, sometimes not, and you hand your lookups to another operator. Switch mainly when your current server is causing trouble.

Will this make my connection slower?

It only changes name lookup, not the line. The download itself does not get faster or slower because of it.