Packet loss reported by check_ping?

[Marc Powell]

> -----Original Message-----
> From: nagios-users-bounces at lists.sourceforge.net [mailto:nagios-users-
> bounces at lists.sourceforge.net] On Behalf Of Jason Byrns
> Sent: Wednesday, December 13, 2006 7:19 AM
> To: Nagios Users
> Subject: [Nagios-users] Packet loss reported by check_ping?
> 
> Good morning, all.
> 
> I've been tweaking our Nagios install over the years.  I've often
> wondered exactly how the check_ping plugin reports its results.
> 
> I used to leave this plugin at the default number of packets, which I
> believe is five.  If and when we saw warnings on packet loss, it would
> usually give us numbers like 16%, 32%, or multiples like that.  Why
not
> multiples of 20%, given that it tried five packets?

check_ping is just a wrapper for /bin/ping (or its equivalent on your
machine). check_ping doesn't change the results of /bin/ping so the
percentages are coming from ping, not check_ping. Do you see the same
results with /bin/ping? Run it in verbose mode to see the ping command
it's using --

$ ./check_ping -v -v  -H 172.27.0.3 -w 10,50% -c 20,70%
CMD: /bin/ping -n -U -w 10 -c 5 172.27.0.3
PING OK - Packet loss = 0%, RTA = 0.21 ms
10.000000:50% 20.000000:70%

> But I still see some reports of packet loss.  Like, 50% is a common
> number I now see.  HOW is it seeing anything but either 0% or 100%
> packet loss, if it uses only one packet per host check??

See above.
 
> Also, along those lines...  I recently moved from the 1.2 Nagios to
the
> more recent 2.4-2.5 Nagios.  Nagios 1.X seemed to only trigger a host
> check if a service check failed.  Nagios 2.X seems to ALWAYS run host
> checks in addition to service checks.  The fact that host checks are
> currently not run in parallel seems like this can really limit
> performance.
> 
> Why did that behavior change?  Will host checks be run in parallel for

Because _you_ configured Nagios to do it. Regularly scheduled host
checks are not enabled by default and are in fact quite discouraged. 

http://nagios.sourceforge.net/docs/2_0/xodtemplate.html#host

"check_interval: 	NOTE: Do NOT enable regularly scheduled checks
of a host unless you absolutely need to! Host checks are already
performed on-demand when necessary, so there are few times when
regularly scheduled checks would be needed. Regularly scheduled host
checks can negatively impact performance - see the performance tuning
tips for more information. This directive is used to define the number
of "time units" between regularly scheduled checks of the host. Unless
you've changed the interval_length directive from the default value of
60, this number will mean minutes. More information on this value can be
found in the check scheduling documentation."

> the 3.0 series, like I think I read once...?

Yes, and they'll actually be of benefit then. See the NetWays
presentations linked off of http://www.nagios.org for more information
on where Nagios is headed.

--
Marc

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