Cached results - No route to host

[Frost, Mark {BIS}]

Ollie,

In situations like these, I tend to go look up the actual command that Nagios is running (Configuration -> Services, say) and then run the command directly from a prompt on the Nagios server and try to debug that way.   While I can't see how all the services on this particular host are running, it's generally a good sign that the other checks are running OK.

What about the possibility of some DNS issue?   Like this host you're checking somehow has 2 IP addresses only one of which is accessible from the Nagios server?    That would be a situation that could be fairly easy to verify when running the command directly from the command prompt and possibly substitution IP addresses.

I'm not aware of ever having seen an issue where something is cached within Nagios and is causing a problem, but we've definitely seen situations where OS issues like DNS, caching with nscd or even local /etc/hosts file entries have caused unexpected results.

Mark

From: Ollie Campbell [mailto:Ollie.Campbell at bbh.co.uk]
Sent: Wednesday, October 17, 2012 4:31 AM
To: Nagios Users List
Subject: [Nagios-users] Cached results - No route to host

Hello,

We have a Nagios v3.3.1 installation running on Fedora. Yesterday we had a power outage which caused Nagios to forcibly power off. It was back up within a few hours but has not been reporting back correctly.

95% of checks on all hosts are fine, but some checks are complaining about 'no route to host'. If I force a rescheduled check on the services that are complaining everything goes back to being 'OK' once again.

I've tried restarting Nagios, clearing the objects.cache. I can of course do this for all the problematic checks but want to know if there is a quicker way or if this is a bug.

I've attached an example of what I mean.

[cid:image001.png at 01CDAC43.CD116CF0]


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