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FAQ Database : Nagios : Configuration

Title:Host dependencies versus parent/child relationships
FAQ ID:F0145
Submitted By:Tom De Blende 
Last Updated:06/02/2009

Description:

How do I configure host dependencies?

Why doesn't my Status Map refelect my network setup (even after configuring host dependencies)?

Why do I keep getting messages of remote hosts being down when the network device between them and the Nagios box goes down, even if I configured host dependencies?  


Solution:

There is a lot of confusion on host dependencies. It is vital to know and understand the difference between host dependencies and parent/child relationships.

A host dependency has got nothing to do with the way your network is setup. It is merely a dependency of one host upon another. So, if host B is dependent on host A, and host A goes down, no host notifications will be sent out for host B. This is not to say that host B is one hop further away from the Nagios box on network level. They can be in the same network segment, even on the same hub. This is also the reason why host dependencies have no influence on the reflection of your network topology in your Status Map.

It's different with parent/child relationships. These kind of relationships are used to reflect the network setup. If host A is a parent of host B, and host A goes down, all notifications for host B will be supressed until host A comes back to earth again. Host A would typically be a router or a switch.

You should read http://nagios.sourceforge.net/docs/1_0/dependencies.html and http://nagios.sourceforge.net/docs/1_0/networkreachability.html for a better understanding. 


Keywords:host dependencies parent child router remote