I have two domain controllers in my domain in remote offices (Europe and China) and two domain controllers in the US, 4 in total. We had a network outage in our US office a few weeks back and during this time, the office in Europe and China experienced issues with DNS not working. I believe part of the issue is that the China server had no forwarder IP addresses set up and the Europe Server did, but it was for our local US ISP.
I want to play around with making some changes to the IP addresses of the DNS Forwarders on these servers but I'm unsure how to test if my changes fix the issue. I would like to avoid disconnecting these remote DC's from our primary DNS servers here in the US. Since everything is up and running well now, if I do nslookup to a website or visit a website in a browser, it will just use our primary DNS servers - how can I specifically test if the DNS forwarder IP addresses are working?
Thanks in advance, let me know if I can give more info or clarify anything