Welcome to CheckDNS!
What is CheckDNS ?
CheckDNS is a tool to test DNS zone hosting, mail and web servers.
Enter your domain name above (for example, "yourdomain.com") and you'll get a
report showing possible problems with this domain.
A bit of history and background.
Once we spent a lot of time to detect and fight such DNS-related problems.
Imagine typical situation: as a systems administrator, you register new domain
name (say, yourdomain.com), configure primary and secondary DNS servers, set up
mail server to receive mails, make www.yourdomain.com to point to your
web-server - a lot of easy steps. So easy that nobody is willing to spend
enough time doing it.
However, one of Murphy's Laws says: "If anything can go wrong, it will. If
anything just cannot go wrong, it will anyway". You can mistype name of mail
server or name of secondary DNS. Another time your firewall can be blocking
requests to name servers, so www.yourdomain.com doesn't open from "outside".
And so on.
Hosted domain can work fine, but have problems in background - sometimes DNS is
too reliable. Typical examples:
- In company X, backup MX (mail server) was configured wrong. Everything was
fine, until mail server #1 crashed. It took one day to bring server back
online. During whole day, backup MX was rejecting all incoming mails as SPAM.
It would be much better to have no backup server at all!
- Another case: company Y didn't know that their primary DNS was not accessible
from the Internet because of firewall configuration, and just secondary was
working. One day secondary DNS was shut down ("it's just secondary, nothing
really important, let's upgrade it now"). Of course, with absolutely unexpected
effect.
-One more: company Z moved primary to another IP, so secondary couldn't refresh
zone copy any more. After expire period, secondary shut down zone
automatically. This was recognised only when primary crashed because of DoS
attack ("But it should have worked without primary, we have backup, don't we
?.")
All these cases illustrate one problem: there is no easy way to diagnose such
problems.
Telnet, nslookup and dig can do the job, but you need lot of time and
attention. Still, it's very much like diagnosing file system problems with disk
sector editor instead of running scandisk or fsck.
So we wanted to create something easy to use but powerful enough, and CheckDNS
was this solution.
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