check_icmp wish list (was: [Nagiosplug-devel] check_ping and check_icmp confusion)

Marc Haber mh+nagiosplug-devel at
Thu Feb 23 02:09:13 CET 2006

On Wed, Feb 22, 2006 at 06:36:03PM +0100, Andreas Ericsson wrote:
> check_icmp had some problems on systems with 32-bit process id's in the 
> early days (causing it to mark the packets wrong and then not 
> recognizing them when they returned). It also used to calculate timings 
> slightly wrong. Both those problems are solved long since, however. Now 
> there are no real reasons to use check_ping instead of check_icmp.

While we're at it: I have recently come across some systems which have
ICMP echo request filtered, but send "host unreachable, administrative
prohibition" back. It would be great if check_icmp could would have a
command line option listing which ICMP packet types are considered a
valid response.

Additionally, it would be good to be able to specify a TTL value so
that one could force a remote host to issue a "TTL exceeded" packet
just in case that "host unreachable" is not configured as well.

for example,, the last hop before the monitored host, is configured to show up in a traceroute, but
doesn't answer to pings at all. That one could be monitored by sending
a ping with the appropriate ttl to the actual host being monitored,
forcing the otherwise silent gateway to answer with "Time to live

$ ping -c 1 -w 10
PING ( 56(84) bytes of data.
--- ping statistics ---
10 packets transmitted, 0 received, 100% packet loss, time 9030ms
$ ping -c 1 -t 8
PING ( 56(84) bytes of data.
>From ( icmp_seq=1 Time to live exceeded
--- ping statistics ---
1 packets transmitted, 0 received, +1 errors, 100% packet loss, time 0ms

This allows host failures to be distinguished from network outages
even in uncooperative networks, which is a nice thing to have and
could be implemented easily in the existing check_icmp code.


Marc Haber         | "I don't trust Computers. They | Mailadresse im Header
Mannheim, Germany  |  lose things."    Winona Ryder | Fon: *49 621 72739834
Nordisch by Nature |  How to make an American Quilt | Fax: *49 621 72739835

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