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it is my third month as a junior sys admin and my senior is on vacation.

Starting this past Tuesday, users have not been able to log in to a website while on our primary network. The web page loads and functions properly, but upon entering credentials, the page just hangs indefinitely. I suspected it was a DNS issue, so I removed the static IP that points to our AD server, rebooted the computer, cleared the DNS cache just to make sure, and tried using 8.8.8.8 and 8.8.4.4. No luck.

I went and plugged the user into our second network and they were able to log in without a problem. Anybody have any suggestions? I'm about to compare packet captures between the two networks to see if there is a problem. Now that I have DNS ruled out, I'm thinking that it might be a firewall issue although inbound traffic from both ISPs pass through the same firewall, and everything was working fine until this week. I contacted the site's admins and they just walked me through basic helpdesk stuff (i.e. clearing history, incognito mode, trying different browsers), but without a doubt this is an issue on our side.

Network Diagram

Dough Roy
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  • You've definitely introduced a new mistake by change DNS settings in a windows domain. Point anything you've changed BACK to your domain controllers and troubleshoot from there. – mfinni Jun 23 '23 at 17:58
  • " although inbound traffic from both ISPs pass through the same firewall" your diagram in fact shows that the backup ISP is NOT using your PIX firewall, so that's where you should be looking for clues. – mfinni Jun 23 '23 at 18:00

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