Interesting DNS problem: hout0101@monit ... / 2013-11-19

Interesting DNS problem:

hout0101@monitoring:~$ getent hosts fg.geo.uu.nl
131.211.64.24   fg.geo.uu.nl
hout0101@monitoring:~$ telnet fg.geo.uu.nl 80
telnet: fg.geo.uu.nl: Name or service not known
fg.geo.uu.nl: Unknown host

Found out after serious searching that this was caused by the /etc/resolv.conf line:

options rotate

Of the 3 available nameservers, numbers 2 and 3 decided to negatively cache fg.geo.uu.nl for good reasons earlier. Options rotate counts per program which means the impact isn't that big for short-lived programs. I guess telnet does a query before querying the nameserver for the needed address to connect to.