Supervise a dial UP host

[Paul L. Allen]

Tom Diehl writes: 

> On Wed, 14 Jan 2004, Andreas Koch wrote:

>> I would supervise a dial-up host with nagios.   
>> 
>> Did this already someone solve?  

> I wish I was good enough to modify the code to do this but alas I am not.

I may be missing something here, because neither of you have been very
clear about what you want to do, why you want to do it, whether the
dial-up has static or dynamic IP and what you're having difficulty
with. 

It depends what you want to do.  If the dial-up has static IP (very
rare these days) then all you have to do is juggle the various
scheduling and timing parameters to match when it ought to be on-line.
This might be very tricky to get right.  Or you disable notification
by e-mail/pager and just keep an eye on the web interface. 

If the dial-up has dynamic IP then life gets harder.  You need some sort
of dynamic DNS service at the very least.  You can do this with nsupdate
(you'd be advised to use the security features to stop malicious people
making changes and in any case you want it to operate on a dedicated
domain or sub-domain reserved for dynamic updates).  You'd need to ensure
that nsupdate is run when the dial-up interface comes up.  If you don't
have nsupdate or a compatible utility, you could do what people providing
dynamic DNS services do and have your own communications protocol for
informing the DNS server that your IP has changed and the daemon running
on the DNS server then runs nsupdate locally. 

That still won't solve the problem of the dial-up machine dies, loses its
connection, somebody else gets the IP address the machine was using - then
some tests (importantly, the ping test to check if the host is up) will
give you OK when in fact the machine you thought you were testing is dead
and you're actually running those tests on a completely different
machine.  So you probably need to at least make the host test something
that requires some sort of authentication, and do as many other tests as
possible using authentication too - such as using check_by_ssh.  Or
have the dial-up machine run some sort of heartbeat protocol (which you'd
have to write) so that if the heartbeat stops the DNS server deletes its
A record. 

Or you install nagios on the dial-up machine itself and have it submit
passive service checks to the main nagios monitor using ncsa, then you
don't need dynamic DNS because the dial-up machine is submitting reports.
If the dial-up machine is not running *nix then this could be difficult.
I see there is a Windows version of send_ncsa available, so maybe it can
be done - I have no idea if anyone has managed to compile nagios under
Cygwin. 

I suspect that most people who have wanted to do this have looked at the
problems and decided it was too much effort to bother with, so nobody has
come up with a solution.  Or it could just be that you're the only two
who want to do it - most dial-ups have people who initiate the dial-up
and would therefore know of the computer dies without you having to
inform them. 

-- 
Paul Allen
Softflare Support 




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