Occasionally a client contacts me to tell me that something "is down". They tell me that they see "domain cannot be resolved" message. I even asked them to do a ping or nslookup and it said that it could not find DNS entry.
The strange thing is that sometimes this happens to the example.com but webmail.example.com or john.example.com would be working fine and vise-versa. Other domains hosted on the same server would resolve no problem on the client's computer.
Usually this goes back to normal after a few hours or days. I don't see what could be causing this...
This has happened several times to two clients. They live in the same city, but don't know each other. They are on diffierent ISPs. It happened at different times.
Linux 2.6.10-1.771_FC2 #1 Mon Mar 28 00:50:14 EST 2005 i686 athlon i386 GNU/Linux
I wen't through all error and warn message and found two that worry me.
The reason they happen is because Plesk automatically creates DNS entry in such manner. If I create a new account with domain widget.com then Plesk will create one NS entry for that domain with the name ns.widget.com -- not the actual name server.
I edited the NS records manually. I deleted the ns.widget.com and create 2 news ones: ns1.example.ca and ns2.example.ca. The errors went away.
Here are the error messages I get from dnscheck.com. Is that a major problem?
Missing (stealth) nameservers
FAIL: You have one or more missing (stealth) nameservers. The following nameserver(s) are listed (at your nameservers) as nameservers for your domain, but are not listed at the the parent nameservers (therefore, they may or may not get used, depending on whether your DNS servers return them in the authority section for other requests, per RFC2181 5.4.1). You need to make sure that these stealth nameservers are working; if they are not responding, you may have serious problems! The DNS Report will not query these servers, so you need to be very careful that they are working properly.
This is listed as an ERROR because there are some cases where nasty problems can occur (if the TTLs vary from the NS records at the root servers and the NS records point to your own domain, for example).
Missing nameservers 2
ERROR: One or more of the nameservers listed at the parent servers are not listed as NS records at your nameservers. The problem NS records are: