[aclug-L] Re: pppd demand dial woes

["Carl B. Davis" <cdavis@xxxxxxxxxxxxx>]

Greg

I had a similar problem with a similar setup.  I used "tcpdump" to
troubleshoot.  I don't think tcpdump came as part of the basic install.  I
had to acquire it elsewhere.  It allows you to trace the source for calls
that might be triggering the demand dialing.   The command looked like

tcpdump -a 'src or dst 206.53'

It helped me trace my problem to a troublesome client on the network.
Good luck.

Carl



"House, Greg" wrote:

> Hi everyone,
>
> I know some of you have done this before, so perhaps you can
> help me.
>
> I have a Linux system (RedHat 6.2, basic install with a kernel
> update to 2.2.16-3). I set up the pppd demand dial option on it.
> At first I thought it worked right, but later, I noticed that
> it was dialing up at times I didn't expect.
>
> My machine has a local network behind it. This net doesn't need
> access to the internet, but the machine itself needs to be able
> to send outgoing email. I'm not routing packets from my local
> net or ipmasqing. I just want this thing to dial up when I send
> mail or access an address that's not on the 192.168.0.0 network
> (the local net). The problem is that it's dialing up on a lot of local
> network activity.
>
> Here's my pppd options file:
>
> user ghouse
>
> -detach
> modem
> lock
> crtscts
> defaultroute
> asyncmap 0
> demand
> idle 30
>
> I thought perhaps it was due to the defaultroute clause
> so I commented that out. With it that way, it wouldn't EVER
> dial.
>
> I think it probably has to do with DNS lookups from things
> like sendmail and some software my company makes, but I'm
> not completely sure. I installed iptraf a little while ago
> to see if it could help me, but I haven't tried it yet. Does
> it have more readable output then tcpdump?
>
> I think the solution must have something to do with using
> the filtering that pppd provides, but I can't seem to find
> any documentation on what the keywords are.
>
> I could try to set up diald instead, but I've heard it's more
> difficult to configure and I don't want to spend my whole life
> configuring this thing.
>
> One final question. All I _really_ want it to do when it dials
> out is send email. Is there any hook in sendmail (or another
> MTU?) that will let me run a script (like /etc/ppp/ppp-on)
> when someone send's mail?
>
> Thanks,
> Greg
>
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