a99.io | New Generation Agar Site!

[Squirrel]

Sorry to be a dick here, but there's a difference between propagation and actual resolution failure. Nowadays, DNS records update within 4-8 hours.
A nice little tool also: https://www.whatsmydns.net/#A/a99.io
[/quote]

Sorry, your answer is incorrect.  You're not a dick, you're just wrong.

Although you are right that there's a difference between simply failing to resolve an IP and propagation. But 95% of all resolution failures occurs because there was a change in a servers/mneumonic DNS (A record), that the DNS server you use, just doesn't know about yet, and is in no hurry to look for an updated value.

You can often skirt past the problem of your ISP not updating records if it's a longer value (48 hrs, I kid you not). Some may well choose 4 hrs or 8 hrs, that is up to them. But, as I said, much of that can be mitigated by changing the TTL on the Authoritative Server several days in advance to something as low as even 300 (5 mins), and that means many DNS servers by old-school ISP's (ie: the one I work for) will be checking for new DNS updates every 5 mins. It really adds only maybe 80ms to the average DNS lookup. And that doesn't cause lag either, since DNS uses UDP, instead of TCP, and is unnumbered (it doesn't need a response).

To skirt the issue of long delays in propagation, you can manually issue commands through a UNIX host, verify the authoritative DNS server IP, then lookup against that DNS server, put the answer into your own DNS server via force, and then have DNS requests go to your server instead. But you would have to re-do that process for every different host/mneunmonic under the same domain, so it would take a bit of a script to accomplish.

It's good to know a layman's DNS tool... But most of them do not ensure accurate results. I would never use one, unless I didn't have access to my own.