0

I'm trying to figure out how DNS resolution works on Windows. I have a PC with two NICs, each one linked to a different LAN (basically the first one is connected to the internet and the other one to the company network). Each of these NICs have a different domain and DNS configured : the first one has the ISP's default and the second one the company private domain and DNS Server. Resolving domains on the internet works fine, as well as resolving FQDN for the private DNS.

However, if I try to ping only hostnames (of devices on the company network), Windows only tries to resolve names on the ISP's DNS which results on a timeout. From the documentation I found on internet, I've read that Windows is supposed to ask the primary DNS and if it does not get an answer, tries the DNS on the other interfaces. It does not seem to be the case though. Did I miss something ? Does windows considers a negative answer from the primary DNS server as a definitive answer ? I don't think it is about prioritising one NIC or the other since it won't ever asks the secondary DNS.

1
  • Does windows considers a negative answer from the primary DNS server as a definitive answer? - Yes. A negative answer is an answer nonetheless. I've read that Windows is supposed to ask the primary DNS and if it does not get an answer, tries the DNS on the other interfaces. It does not seem to be the case though - You got an answer. An NXDOMAIN is a valid answer. – joeqwerty Mar 6 '20 at 12:39
1

https://docs.microsoft.com/en-us/archive/blogs/stdqry/dns-clients-and-timeouts-part-1

The actual behavior of the DNS client is that it is going to query its DNS servers in the order that they are listed until an answer, either positive or negative, is received. Once an answer is received, either positive or negative, the DNS client stops the query process and gives that answer back to the calling application. Only when a query to a DNS server times-out (or reports a server error) is when the client retries the query with the next DNS server in the list. In other words: negative answers do not trigger retries with alternate DNS servers, only timeouts (and other errors) do.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.