Host dependencies


I’ve setup host dependencies for all my devices but I still get host down alerts/notifications from dependent hosts. Do I need to set up parents in the hosts? Or do I need to setup service hosts?



I personally hate using host dependencies. I prefer to setup parents in the hosts.cfg file.
When you look at my status map, you can see that there is a connection from eth0 on my nagios box, to a host which is the switch port, which connects to the switch, which connects to another port on that switch, which connects to a port on another switch, and so on. That way, if a cable/host/router/switch/whatever goes down, I only get ONE alert, showing exactly where the blockage is taking place. All hosts after that point, are simply unreachable. It takes nagios far less time to determine the blockage using parents, rather that dependancies. It took far too long with dependancies.


The problem with alot of monitoring tools, nagios included, is that if you have 100 servers that you want to monitor, if a switch goes down, you could get 100 alerts about 100 hosts being down. Which is not true. The only thing that is down is a switch, or a cable is unplugged. Setting up host dependancies or even parents is not practical for monitoring 100 servers/hosts since actually, one host does NOT depend on the other. There is no reason why boxA would be needed in order to ping boxB. So parents nor dependancies will do you NO GOOD, unless they truely are parents/dependant. In my nagios setup, since I have the entire network mapped out, the ports, the switches, the port used to connect to serverA and it’s interace eth0, it’s obvious that parents are valid. ServerA does not have a perent of ServerB, but it does have a parent of ServerA-eth0 which is it’s interface card. That ServerA-eth0 host has a parent of the port on the switch it’s connected to named SwitchA-port10 and so on.