It’s Always DNS: A Horror Story

DNSI’ve been an IT consultant for nearly 15 years. During that time, I’ve run across countless horror shows involving all manner of outages and technical glitches that plunged me into the depths of megs and megs of packet captures and process monitor traces. This resulted in hours and hours of lost time chasing the “ghost in the machine.”

However, if you’ve been around long enough, you’ve learned that the worst horrors are manmade.

When I was a young, freshly minted consultant, I came across one of my first horror stories. As you can infer, it was DNS and it was manmade.

I received a call from a new client. He asked me to come over ASAP because there were problems with his Exchange server.

“Okay, I’m packing up and headed to my car, can you send me an email with a quick rundow— oh. Sorry. Can you give me a quick verbal rundown while I head to the car?” I asked.

The issue was that users couldn’t send email. I thought to myself it shouldn’t be too bad to fix.

When I got there, I logged into Exchange and confirmed services were running. The databases were mounted. I could send mail via the Outlook Web App. Hmmmm. Netstat showed all the proper ports listening. I asked some users to test, and it was still a bust. I reconfigured my Outlook client to use the Exchange server and it worked. I used an impacted user’s account. Still good.

I decided to hop on an impacted user’s computer and test. I sent an email and it bounced. The bounce message indicated SMTP relay is denied. SMTP? This was a domain joined Windows 2000 desktop using Outlook. Why are they using SMTP…? I then dug in to their configuration. They were also Popping mail, but the hoot was that the SMTP server was set to smtp.att.net. Hmmm ….

I then discovered the end users were not rebooting their machines because they would hang when applying group policies.

Eureka!

“Say, do you mind if have a look at your computer?” I asked.

ipconfig/ all to the rescue!

The DNS server was set to 4.2.2.2. There was my problem. I changed the DNS configuration.

Rebooted and it flew. User logged on and again, it flew. By this time, I’ve fixed a lot of pain. The client wanted me to make any other changes I needed to make. I switched Outlook from POP/SMTP to MAPI.  Holy cow!

In the words of the best AD and Exchange person I know, “It’s always DNS.” DNS is something too many take for granted. Most of the time you can point to a DNS server and things will “kind of” work, but in the long run you’ll end up with all manner of issues. When name resolution is simply broken, that’s one thing, but sometimes, it’s misconfigured just enough to cause a whole bunch of problems.

If you’re having unusual problems like this, check your DNS. If you want help, email or call us at 502-240-0404!