Question regarding Dependencies

[Dale Hobbs]

Thanks Darren that clears things up immensely. 

 

One more question for you then. Say I have one server that has 6
services being checked. If that server goes down then I don't want to be
notified that the other 6 services are down as well. Would I use service
dependencies for this?

 

-----Original Message-----
From: Darren.Lichty at alltel.com [mailto:Darren.Lichty at alltel.com] 
Sent: Thursday, August 19, 2004 7:51 PM
To: Dale Hobbs; nagios-users at lists.sourceforge.net
Subject: RE: [Nagios-users] Question regarding Dependencies

 

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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