Question

I’m creating my own DNS server using Windows Server and other users will use my DNS server and thought that if it will go down I should have a backup how about if users set my DNS as Primary and Secondary can be something like google public dns? How will it will work? If it can’t resolve using my DNS it will try google’s? It will try it every request?

Answer 1

Since you mention Google’s public DNS server, I assume you’re talking about a nameserver to be used as a recursive resolver (not as an authoritative server containing zones).

DNS doesn’t distinguish between “primary” and “secondary” nameservers. What actually happens is up to the client.

Some clients may query nameservers in order, so they will query yours first, and then query Google’s only if they don’t get a response from yours. Other clients may choose a random server from the list for each query, so they will sometimes query yours and sometimes query Google’s. Still others might track statistics on each nameserver and prefer the one that usually gives a faster response. This last options requires a stateful client and it’s something another nameserver acting as a forwarder might do.

In practice it will not matter because your recursive resolver and Google’s public recursive resolver should give the same response for every query.