DNS server slow, not resolving all sites

Question

We have two servers running DNS under Windows Server 2012. Today, many sites are resolving slowly (it says 'Resolving host' for a long time when you try to access them) and some sites and services don't resolve at all. When I set the DNS servers on my PC to 8.8.8.8, every address resolves fine, so it must be a problem with our servers.

I've tried restarting the DNS and ADDS services and clearing the cache on both servers, but this did not solve the problem.

Answer 1

Please run;

Dcdiag /v /c /d /e /s:%computername% >c:\dcdiag.log
repadmin /showrepl >C:\repl.txt
ipconfig /all > C:\dc1.txt
ipconfig /all > C:\dc2.txt
(etc. as other DC's exist)
ipconfig /all > C:\problemworkstation.txt

then put unzipped text files up on OneDrive and share a link.

--please don't forget to Accept as answer if the reply is helpful--

Answer 2

I tried adding 8.8.8.8 as a forwarder on the server, and that solved it. It looks like the issue is related to our servers trying to communicate with our ISP's DNS server. When I set our ISP's server as the DNS server on my PC, it works fine.

Answer 3

@Nicholas94 Hi,

Thank you for posting in Q&A!

I want to confirm that the sites your DNS servers failed to resolve are internal resources or public resources? If they're public sites,it's a normal phenomenon. Because the DNS server must be configured a public forwarder to access external resources.

(1) A forwarding only occurs in case where the DNS server cannot resolve a query by using its own data and local cache. Usually this happens when a query comes in for an external name that is outside the configured zones in a DNS server.

(2) DNS Server will contact Root Hints only when it no Forwarders available or when Forwarders cannot resolve the query. This makes the process of name resolution using Root Hints to be longer.

For more details, please refer to:
https://www.mustbegeek.com/understanding-dns-forwarders-and-root-hints-in-windows-dns-server/#.X3QcVGgzaUk

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