monitoring unreachable hosts

[Johannes Dagemark]

Hi Mark

Frost, Mark {PBG} wrote:
> This topic of unreachable hosts that's come up recently has got me
> thinking about an issue we have.  We have a few hosts that are behind
> proxies and as such are impossible to ping.  They have a single service
> which we can check through the proxy successfully.
>
>   
Why not simply use this check then as the host check as well as the 
service check?

Cheers
Johannes

> I'm a little stuck on what to do with the host checks.  I can supress
> the alerts, but they still always show as critical (kind of permanently
> critical).  Maybe I'm too anal, but I don't like that.  It's
> meaningless.  So I was thinking of making the host check command
> identical to the service check command.  The end result being that if
> the service is up, the host will also show up, if the service is down,
> the host will also show down.  Still weird, but at least kind of
> conceptually correct.
>
> What concerns me about is the my understanding of how host and service
> checks would work in this case.  If the service check fails, it's going
> to want to fallback and try the host check which will fail also because
> it's running the exact same check as the service.  However,  what if
> I've disabled notfications on the host itself?  That is, I really only
> ever want service alerts -- no host alerts.  In the case of a normal set
> of host/service checks, Nagios will notice that the host is down,
> suppress alerts about all the services being down and send out only a
> "host is down" alert.
>
> In the scenario where the host and service checks are the same and the
> host notifications are disabled, wouldn't a service alert be suppressed
> and I'd never hear about an issue on this host?  Again, conceptually,
> the service result is all that's meaningful.  Maybe Nagios is smarter
> than that and would decide that since the host notifications were
> disabled that it would go ahead and send the service alerts anyway?  I
> guess this could be an issue with any host that has notifications
> disabled now that I think about it.
>
> I tried earlier to disable all checking of the host in this case and
> that gives me a host unreachable alert when the service goes down.  That
> makes sense since the host can't be checked, but I don't want it going
> into that bogus state.
>
> What would probably be ideal is if Nagios had some way of marking a host
> as being irrelevanet.  That is, the service would sort of stand alone
> without any host dependency in terms of monitoring.  Kind of strange,
> though.
>
> Thanks
>
> Mark
>
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-- 
Johannes Dagemark
CTO / VP Engineering
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