[Nagiosplug-devel] Feature request: extend check_ping to specify source address

John P. Rouillard rouilj at cs.umb.edu
Fri Jul 18 15:34:57 CEST 2008

In message <488044D7.1070001 at op5.se>,
Andreas Ericsson writes:
>Dave Horsfall wrote:
>> On Thu, 17 Jul 2008, Matthias Eble wrote:
>>> this feature is already provided by check_icmp.
>> Err, how?
>It isn't, and I fail to see how that could work at all.
>check_icmp and ping alike mark their packets with pid, sequence-number,
>host-id (decided internally) etc, etc. Modifying the ip->src_addr field
>would cause the targeted host to send its ICMP_ECHO_REPLY packets to a
>different host, so check_icmp (or ping) wouldn't be able to pick them
>up at a later time.

Well you set the source address to one of the ip addresses on the box.

>Otoh, it's not hard to implement, so convince me it's needed and I'll
>add it :-)

I don't have any systems like this now, but imagine a multihomed host
on a routed network.

One interface at ip allows direct access to the host,
while interface B on allows access to via some set of
routers starting with

Unless you can set the source address, (which I assume also selects
the network interface the ping goes out), you have no way to test the
connectivity to the network from the box via the
routers starting at

				-- rouilj
John Rouillard
My employers don't acknowledge my existence much less my opinions.

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