[Nagiosplug-help] check_icmp oddness

Israel Brewster israel at frontierflying.com
Wed Apr 9 20:28:16 CEST 2008

On Apr 9, 2008, at 12:18 AM, Andreas Ericsson wrote:
> Israel Brewster wrote:
>> On Apr 4, 2008, at 1:42 AM, Andreas Ericsson wrote:
>>> Israel Brewster wrote:
>>>> I am having some difficulty using the check_icmp plugin to  
>>>> monitor a  number of my hosts, specifically Linksys RV082 routers  
>>>> running the  latest firmware. What's happening is if I have a  
>>>> command line such as:
>>>> ./check_icmp -n 2 -m 1 -w 3000,80% -c 5000,100% xx.xxx.xxx.111   
>>>> xx.xxx.xxx.33
>>> Add '-i 0.5s' to the command line and it might just magically start
>>> working. That will increase the packet interval, which can sometimes
>>> be too short when sending to a single host with multiple IP's.
>>> Especially if there's a firewall in between.
>> Well, that partially worked. If I increase that value to a  
>> ridiculously high amount (>10s) the packet loss drops to only about  
>> 33% (with 5 pings) rather than the 60% I get with the default  
>> settings. The pattern, however, is the same- only the first x  
>> packets received, where x is a constant in relation to the number  
>> of packets sent. One thing I find a bit confusing- the help text  
>> lists the -i switch as the "MAX packet interval". What determines  
>> the min? I would thing the minimum packet interval would be more of  
>> an issue than the maximum, although perhaps not considering that  
>> setting the maximum did make a difference. Thanks again!
> The minimum packet interval is determined as "if we've already seen
> replies to all packets we sent to this host, it's probably ready to
> get another one, so send it out instantly."

I'm wondering if it isn't this exact logic that is causing my  
problems. Is there any way to change this? -I does not help- see below.

> -I (capital i) is used to set a target_interval, which is used as
> the minimum value to wait between two packets going to the same
> target.

The capital i switch does in fact exist on the check_icmp plugin I  
have, however it is described (as mentioned in another reply to this  
thread) as MAX target interval, not min. Indeed, I can set this number  
up as high as I want (I  tried values up to 300,000), and it doesn't  
increase the execution time. If the plugin was sending 5 pings and  
waiting 300,000ms between pings, it should take about 20 minutes to  
complete. Therefore, that -I switch is obviously not setting  the  
minimum value to wait between two packets going to the same host.  
Additionally, while this switch, like the -i switch when doing  
multiple hosts, does improve things (check_icmp packet loss drops to  
33% rather than 60%) it doesn't actually fix anything. Thanks again  
for the suggestions and time on this issue.

Israel Brewster
Computer Support Technician
Frontier Flying Service Inc.
5245 Airport Industrial Rd
Fairbanks, AK 99709
(907) 450-7250 x293
> I'm not sure if that switch exists in the check_icmp.c the
> nagiosplug project ships, but it does in the one I've got.
> -- 
> Andreas Ericsson                   andreas.ericsson at op5.se
> OP5 AB                             www.op5.se
> Tel: +46 8-230225                  Fax: +46 8-230231

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