Passive checks with NSCA

[Marc Powell]

> -----Original Message-----
> From: Colin A. White [mailto:colin at trematon.com]
> Sent: Thursday, December 04, 2003 10:55 AM
> To: 'nagios-users at lists.sourceforge.net'
> Subject: [Nagios-users] Passive checks with NSCA
> 
> Greetings all,
> 
> I was wondering if anyone could give me a quick sanity check before I
> dive in and break my Nagios install...
> 
> I'm hoping to deploy the nsca addon (and send_nsca) to passively
monitor
> two debian devices hanging off the end of a DSL line.  i.e. the target
> hosts have dynamic private IPs and do not have resolvable hostnames.
I'm
> aiming to log snmp traps only.  Am I right to think this is a 'passive
> check of a volatile service' in nagios-speak ?

Yep.

> 
> I'm wondering now, how to correctly configure the object files for
these
> hosts and their passive services.    I notice from the docs "that in
> order to submit passive service checks to Nagios, a service must have
> already been defined in the object configuration file"  Is this
proposed
> service definition sane??
> 
> define service{
>         host_name                               unknown
>         service_description                 TRAP
>         check_command                    check-host-alive
>         is_volatile                             1
>         active_checks_enabled         0
>         passive_checks_enabled       1
>         check_period                        none
>         max_check_attempts            1
>         normal_check_interval          1
>         retry_check_interval              1
>         notifications_enabled             1
>         notification_interval                31536000
>         notification_period                24x7
>         notification_options                w,u,c,r
>         contact_groups                      linux-admins
>         }

You must define the service in Nagios so it knows that the passive check
isn't bogus. I would use a more descriptive host_name above. Think of it
as a label, not as a DNS name. The check_command is fine, it'll never
get executed. For a cleaner web interface (without the big red 'X'),
consider setting active_checks_enabled to 1 and leaving the check_period
set to none. That's a personal preference however.
 
> I'm also wondering how to handle the hosts.cfg definition which
requires
> an address param as a mandatory field...??  It's this 'gotcha' that
has
> me most stumped.  Am I able to use an arbitrary or fake IP and simply
> use host_name matching to determin whether to accept and log the trap?

You can use an arbitrary IP (127.0.0.1 for example). If you don't define
a check_command in your host block, the IP will never be used ofr
anything. Nagios uses the host_name (label) and service_description to
make all internal associations and decide whether to accept or ignore
the passive check.


If you haven't read it,
http://nagios.sourceforge.net/docs/1_0/int-snmptrap.html might be useful
to you.

--
Marc


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