Multiple interfaces, multiple parents

[Andreas Ericsson]

Tobias Klausmann wrote:
> Hi! 
> 
> On Tue, 27 May 2008, Hugo van der Kooij wrote:
>>> Unfortunately, Nagios connects multiple parent hosts with
>>> logical AND, which means that the host only turns UNREACHABLE
>>> when *both* switches are gone.
>> The funny thing with redundant paths is that they are in fact
>> redundant. So if you loose one you still have connectivity and
>> nothing becomes unreachable.
>>
>> So where is the flaw in this design in Nagios? If breaking a
>> single link ~ will result in something becoming unreachable
>> then you do not have true redundancy.
> 
> Oh, the machines themselves aren't connected redundantly, only
> the switches themselves are. Usually the second link is used for
> connections to database machines and the like. As such, if either
> links goes down, the machine goes down (from a can-do-its-job
> perspective). Yes, I can still reach the machine (on convoluted
> paths since the backend nets are not routed).
> 
> What I'm after is making a failing switch visible to the admins
> of such machines (and ideally everybody else), so I'm aiming for
> the distinction of DOWN vs. UNREACHABLE.
> 

Would you settle for DOWN vs CRITICAL? If so, monitor the secondary
interface as a service.

> I don't really want to make all the switches visible to all
> admins via the web interface (and I doubt they all are able to
> tell which switch is "theirs" just by the names).
> 
> I don't see this behaviour as a *flaw* in Nagios, it's just
> unfortunate for me that it works this way and I had hoped there
> was a way around it.
> 

There is. Either add the switches twice, calling the switches
added with their secondary interface, <switch-name>-srvint
(or some such - I'm thinking "admin interface" and "service
interface" here), or add the secondary interface as a service.

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

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