Question regarding Dependencies

[Darren.Lichty at alltel.com]

Dale:
I believe what you are looking for is a parent-child relationship, rather than a host-dependency.
 
Given the following network (forgive the ASCII art ;-) ):
            Nagios
                |
           Firewall
                |
        *-------*-------*
        |       |       |
        A     B     C

I would set this up as:
        define host{
                host_name       A
                parent          Firewall
        }
 
        define host{
                host_name       B
                parent          Firewall
        }
 
        define host{
                host_name       C
                parent          Firewall
        }

        define host{
                host_name       Firewall
        }

You will note that there is no parent defined for 'Firewall'.  This is because 'Firewall' is local to Nagios (meaning, no the same network/subnet).
 
In this case, if any of 'A','B', or 'C' goes down, Nagios will check 'Firewall'.  If 'Firewall' is down, Nagios will tell you about it, but NOT about 'A', 'B', or 'C' ('Firewall's children).  This will show up in the web interface as a 'network outage', instead of a simple 'host' outage.
 
I do not use host dependencies personally, so I could not comment as to a scenario in which they would be useful.
 
Important note however, if you want 'Firewall' to be checked ONLY when any of it's children are down, do not define any services for this host.  If, however, you want Nagios to "active" check this device, setup a simple 'check_ping' service for it.  I have not completely tested this out, but I do believe that having an "active" check on firewall in this configuration will allow Nagios to pick up a failure on that device quicker (this may not be the case thought).
 
I hope that helps.
 
-Darren
 
-----Original Message-----
From: nagios-users-admin at lists.sourceforge.net [mailto:nagios-users-admin at lists.sourceforge.net]On Behalf Of Dale Hobbs
Sent: Thursday, August 19, 2004 11:14 AM
To: nagios-users at lists.sourceforge.net
Subject: [Nagios-users] Question regarding Dependencies



For give me if this question has been asked before. I have read the docs in regards to dependencies but am still a bit unclear as to the internal workings.

 

If I have 3 servers (www1, www2, www3) on the outside of my firewall with the following dependencies set up for each of the 3 servers:

 

define hostdependency{

        host_name                       www1

        dependent_host_name        firewall

        notification_failure_criteria   d,u

        }

 

If my firewall goes down, obviously it will notify me that the firewall is down but will it also notify me that it can't contact each of the 3 servers as well? Also if one of the servers goes down is Nagios smart enough to check the firewall first to make sure that it is still available before notifying me that the server is down in case that it can't contact the server because the firewall is down?

 

 

 

Dale Hobbs 
End User Support 
Chancery Software -- The Right Partner. The Right Solution. 
Tel: 604-294-1233 Ext.4744 
Fax: 604-294-2225 
Email: dhobbs at chancery.com 
http://www.chancery.com <http://www.chancery.com/>  

 

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