Dynamic IP adresses - DNS Cache

Troubleshooting
1

Hey there,

I’m using Checkmk 1.6.0p22 raw. I’m monitoring my hosts at home where I have a dynamic IPv6 prefix.

Since the prefix is dynamic I disabled the internal DNS cache.

  1. WATO → Access to Agents → Hosts with dynamic DNS lookup during monitoring
  2. WATO → Global Settings → Use DNS lookup cache → no

Every once in a while my IPv6 prefix changes and everything breaks.

If I look at $site/etc/nagios/conf.d/check_mk_objects.cfg this file contains a cache of the IP addresses which should be disabled by those settings.

I have to save a host and reload checkmk to get a working config again.

Is this a bug? Is there a better way to solve dynamic IP addresses?

Thanks.

2

No - how does you host config looks like? Is the IP field empty?
You need to fill the IP field with the FQDN or shortname then the monitoring core needs to resolve the address at every check time.
In your case the resolving happens only on config generation time.
You can verify this if you do a “cmk -R” after the break happens then all should be fine again.

3

I left the IP field as default (empty).

I think I have to fill the IP field with the FQDN - I did similar things with Icinga 2.

I’m thinking about reloading Checkmk on IP address changes, using the FQDNs breaks some other checks.

4

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