We recently decided, okay, I am the a$$ who decided to test in sandbox whether or not to implement ManageEngines MDM Free Hosted Software. While my IT staff was setting this up on the server, and made the proper port allowances for the ME MDM, something strange happened.
Side story, I am spending time this week with my daughter, whose 12 and don't see much (she's in NJ and I am in Tx). So, I left early for her. When I noticed I am getting calls from my COO, and clients I deal with directly, that cannot access their web pages. So, I try to submit a ticket, cannot get to the ticket page, I remote into my office computer to use the internal link, that works.
So, then I have a discussion with my IT manager, and he's telling me everything he has done, I even ask him about the codes in directly in the DNS. I return to work with my daughter, promising we won't be long. So, the issue is:
- DNS is working
- We tried to stop/start the DNS
- We even rebooted the server (not fun)
- All internal links were working
- All requests that need be forwarded from the DNS work
- The only DNS failing was the items stored on the web server
So, there is me with 20 years in IT, my IT Manager and his staff with a wide range of certs and education looking in to different scenarios that can be causing this. Meanwhile, my daughter says, "Could it be something with a firewall?" Just as my IT Mgr was getting ready to say that he checked necessary ports, like he told me...I said, "Did you make the adjustment to the hardware FW, or a subordinate?" He implied a subordinate. I said, "Show me the firewall."
Soon as he brought up the port listings there it was, the webserver address accidentally got changed and was pointing to the wrong server for internet calls. We immediately fixed the problem, broke the fingers of the subordinate, and I instrumented a new policy of allowing "little girls in the war room". Side note, my daughter received a consulting fee of a Red Lobster dinner for that. 
