Passive service checks via NSCA and requir ed check command defini tion

Paul L. Allen pla at softflare.com
Mon Aug 8 17:54:45 CEST 2005


Ralph.Grothe at itdz-berlin.de writes: 

>> If there is a problem with something prior to crond starting crond may
>> not get started but everything you're monitoring on that server is 
>> started. 
> 
> You're absolutely right.
> It was a bit short sighted by me.

Of course, you can use check_procs to monitor that crond is running.  But
there are probably even more exotic scenarios where crond is running but
you're not getting check results from the plugin (such as an error in
the plugin which means it always returns OK, to name but one). 

> Ah firewalls, another of my monitoring intentions oponents.

That's the main reason NSCA exists - so you can install nagios on the
firewall or on one of the machines behind the firewall instead of
trying to persuade the firewall admin to open up various ports.
Check_by_ssh is an alternative, if you can ssh onto the firewall or one
of the machines behind the firewall. 

> Even worse with ours. Firewall admins seem (for paranoia reasons?) to
> silently drop all ICMP packets from even ingress (no not the database ;-)
> traffic, what to me seems counterproductive to ICMP's original objective.

Dropping all ICMP may cause problems with MTU path discovery, but that's
their problem.  Dropping pings means you can't check the firewall or
the hosts behind it to see if they're up.  I believe nagios 2.x supports
passive host checks but 1.x doesn't.  Well, one bit of the docs says it's
impossible but another bit says it's possible but too complicated to
explain. 

> very scattered and disjoint indeed

Feel free to write a "HOWTO" on setting up passive monitoring that gathers
it all in one place.  Even if you can't persuade Ethan to add it to the
docs I imagine nagiosexchange would accept it. 

-- 
Paul Allen
Softflare Support 




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