circular parent/child chain

[Andreas Ericsson]

On 11/19/2012 07:57 PM, Lucy Pelzer wrote:
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> 
> Hi List,
> 
> thanks for your fast replies, but I think you missed my point. I know
> that I could configure one parent and alert about spanning tree or do a
> lot of other stuff, but this would not help me at all in the following
> situations.
> 
> Lets say that I have a lot of important infrastructure behind switch-4
> and switch-5 and that the "normal" stp way is to route through switch-2
> for switch-5 and for switch-4 to switch-3. Lets also suggest that at
> switch-2 there is not that much important infrastructure. If now
> switch-2 is failing at the same time a really important infrastructure
> behind switch-5 fails. I will only get informed that switch-2 failed,
> because switch-5 is a child of switch-2, but I will not be informed
> about the more important stuff at switch-5. Now I will spend a lot of
> time to exchange switch-2 before I even find out that there is something
> really important at switch-5 going on only because I could not give it a
> second parent (switch-4). Maybe the other problem would have been fixed
> in minutes if I would have known about it. I think it is a bad idea to
> have such parent/child chains. And please keep in mind that this is just
> a simple example and that a network can be much bigger than just 5 switches.
> 
> The other point is that I will never see the real network infrastructure
> in the statusmap. As far as I can read the documentation I should also
> be able to build up my whole infrastructure like it is in the statusmap.
> Or for what is it at all?
> 

parent/child relations are primarily to block notifications for stuff that
is only down because some earlier stage in the traffic shoveling is down.

> I would be really pleased if somebody could answer my question.
> 
> - - Why is it in nagios not possible to be parent/child of a other host at
> the same time?
> - - Why is it a deadlock and where is the problem?
> 

Because if A is a parent of B and B is a parent of A we'd never run out
of parents to check when trying to determine the root cause of the
problem.

-- 
Andreas Ericsson                   andreas.ericsson at op5.se
OP5 AB                             www.op5.se
Tel: +46 8-230225                  Fax: +46 8-230231

Considering the successes of the wars on alcohol, poverty, drugs and
terror, I think we should give some serious thought to declaring war
on peace.

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