DNS Troubleshooting on Windows: When the Internet Works but the Intranet Doesn’t

One of the more frustrating problems in IT is when a user says: “The internet works, but this one internal site doesn’t.” At first, it sounds simple. Public websites load fine. Email works. Teams works. But the internal app still refuses to open, or it loads painfully slowly. In situations like that, the application itself is not always the real problem. Quite often, the issue is one layer lower: DNS. That is also why I think DNS is worth understanding in a practical way, not just as a protocol you read about once and then forget. In day-to-day admin work, name resolution problems show up more often than people expect. A very typical scenario Let’s take a neutral example. A user tries to open: http://intranet-app01/portal What they see is something like this: the page does not open at all, or takes too long to load, public websites still work, nslookup intranet-app01 returns an IP address, but the internal application still behaves as if something is wrong. At that point, it is very te