parent host relatiionship

[Matt Pounsett]

On Sat, 17 Jan 2004, Ric Moseley wrote:

> No one attempted to answer this so I am sending it again.  
> 
> If I do want to get notifications for hosts that are behind another
> server/router that is down at the time is the 'parents' option in the host
> config the option to use?  When I set that option up to the server/router
> that is in front of the host and then turn off the notifications option of
> 'u' (unreachable) will I not get emails if the router goes down about the
> server behind it going down?

It sounds a bit like you might be confusing two related, but different
features of Nagios.  I'll try and give you a quick rundown on how this works,
from which I think you should be able to pick out the things you need for your
setup.

First, let's assume a simple set of hosts.  The Nagios machine (N),     N
connected to a switch (S) which has two other machines connected in     |
turn to it (A and B).                                                   |
                                                                        S
If you want Nagios to be able to draw you a useful status map,          /\
you should set the "parents" for hosts A and B to S.  This             /  \
indicates to Nagios that, in order to reach A or B, packets must      A    B
flow through S.  

Now, the other option involved here is the 'notification_options'.
Notification option 'D' tells nagios to complain when a host is down.  A host
is down when at least one of its parents are reachable, but it is not.
Notification option 'U' tells nagios to complain when a host is unreachable.
A host is unreachable when all of its parents are either down or unreachable. 
So, if your 'notification_options' for S, A and B are all set to "D,R" (R is
Recovery), and if you were to pull the power on S, you would only be notified
about S being down, since A and B get marked as Unreachable, and you haven't
included the Unreachable option for notification.  If, instead of pulling the
plug on S you left it up and pulled the plug on A and B, then you'd get
notified of A and B being down.

If you also want to be notified when hosts are unreachable, then include the
'U' option in notification_options.

Does that answer your question?

-- 
Matt Pounsett                 CIRA - Canadian Internet Registration Authority
Technical Support Programmer                    350 Sparks Street, Suite 1110
matt.pounsett at cira.ca                                 Ottawa, Ontario, Canada
613.237.5335 ext. 231                                      http://www.cira.ca



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