[Nagiosplug-help] check_icmp problems

[Israel Brewster]

On Aug 26, 2008, at 3:20 AM, Andreas Ericsson wrote:

> Andreas Ericsson wrote:
>> Clever solution. I'll apply it to my version of check_icmp, with  
>> SEQ_BITS
>> increased to 6. That'll allow 64 packets to a single host (I know  
>> some of
>> our customers use 30 for some of their gear), while still making it
>> possible to scan 1024 hosts in one go, which is almost certainly  
>> (still)
>> overkill.
>
> And here's the patched check_icmp.c (from the op5 source-tree).
> Mr. Brewster, can you please try using this version and see if it
> fixes your problems?
>
> Save check_icmp.c on your nagios server somewhere then do this:
> gcc check_icmp.c -Wall -O2 -o check_icmp
> (su to root)
> cp check_icmp /path/to/your/previous/check_icmp
> chmod 4711 /path/to/your/previous/check_icmp
>
>
> You won't need to restart Nagios for the changes to take effect.
> Please report back if it works properly. Thanks :)
>
> -- 
> Andreas Ericsson                   andreas.ericsson at op5.se
> OP5 AB                             www.op5.se
> Tel: +46 8-230225                  Fax: +46 8-230231

Ah, much better, although not totally perfect. Somewhat interesting  
behavior now though- if I leave it on the default of 5 pings (which is  
fine, really) it works mostly perfectly, as long as I don't repeat the  
test too quickly. I do still see an occasional lost packet where there  
should be none, but nothing consistent or major. A value of 6 usually  
works, although the definition of "too quickly" gets broader. By the  
time I get to 7 pings, I start loosing one packet every few test runs,  
regardless of how long I wait between tests. Above 7, and I  
consistently loose one or two packets (but no more than that), even  
when only doing single isolated tests (separated by more than a minute  
or two). Increasing the packet interval to 1 second alleviates this  
problem somewhat, but, of course, removes a large part of the  
advantage of using check_icmp over using check_ping.

So basically, at 5 pings, check_icmp is now usable on the devices  
where before I only got two pings back. For an arbitrary larger number  
of pings, I consistently loose one, or in some cases, two packets, but  
no more. So still improved performance over what it was, but not quite  
perfect. I suspect, however, that with whatever Linksys is doing in  
their firmware that broke things in the first place, this is the best  
we can hope for, and 5 pings is certainly adequate for my purposes, so  
it should be good. Thanks!

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Israel Brewster
Computer Support Technician
Frontier Flying Service Inc.
5245 Airport Industrial Rd
Fairbanks, AK 99709
(907) 450-7250 x293
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