[Xymon] What does the 'dns' test do?

John Horne john.horne at plymouth.ac.uk
Tue Mar 12 16:23:46 CET 2019

On Tue, 2019-03-12 at 13:57 +0000, SebA wrote:
> I don't really understand why you would be negating the dns test on the
> server, rather than just removing it altogether.  You will be slowing down
> xymonnet if you have tests that are getting blocked by firewalls / iptables.
> If you're interested in a test that checks iptables is running, I made a
> simple extension script I might be able to share.
The check is to ensure that the local (client) DNS service is not 'open'. That
is, that it will not resolve queries from external sources. (And hence prevents
amplification attacks.) We run a separate client DNS test to ensure that local
resolution is working, and, of course, a 'proc' check that 'named' is running.

The 'dns' test/ICMP problem has only just appeared when we moved the monitoring
server. But without knowing what it was that the test was trying to resolve
made it a bit difficult to diagnose.


John Horne | Senior Operations Analyst | Technology and Information Services
University of Plymouth | Drake Circus | Plymouth | Devon | PL4 8AA | UK

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