Internet connection sharing

Frank Shute frank at
Sat Jun 14 04:39:41 BST 2003

On Thu, Jun 12, 2003 at 02:46:41AM +0100, Andrew wrote:
> >
> > He'll get a `proper' address assigned by his ISP also but he's also
> > assigned the class C address to the gateway which his Windows machine
> > can see...I think. It's not clear exactly what the address of his
> > Windows machine is but I'm assuming it's on the same class C subnet.
> Quite. I confess to not having a lot of experience with ppp, I'm a little
> bit spoiled on my nice cable connection ;-) Also, I use ipfilter, so have
> never even looked at ipfw/natd! Talk about experienced...

I was originally going to have a dig about all the lucky swines on
this list with their broadband connections not even knowing what a
dial-up ppp connection is ;) 

> > > Also, are you using ipfw/natd or ipfilter/ipnat?
> >
> > ppp(8) has got a -nat switch:
> Aha! That I did not know.

It certainly makes life easier as you can run without a firewall which
makes debugging your ppp connection easier.

<shameful confession>
As it happens, I don't use a firewall & just rely on tcpwrappers ATM &
running hardly any services.

I started writing a load of firewall rules (ipfw) but soon got tired
of it...I'll make an effort again sometime soon...

> >
> >    The -nat flag (or -alias flag for backwards compatibility)
> >    does the equivalent of a ``nat enable yes'', enabling ppp's
> >    network address translation features.  This allows ppp to
> >    act as a NAT or masquerading engine for all machines on an
> >    internal LAN.
> >
> > From natd(8):
> >
> >    This program provides a Network Address Translation
> >    facility for use with divert(4) sockets under FreeBSD.
> >    It is intended for use with NICs - if you want to do NAT
> >    on a PPP link, use the -nat switch to ppp(8).
> >
> > I don't use either but it seems the -nat switch to ppp seems worth a try
> > - assuming it hasn't been tried already.
> Seems like it shouldn't be that problematic. But then, I had loads of
> trouble just maintaining a connection with ppp, kind of put me off it a bit.
> Although that may have been down to the modem,  or the line itself. 

ppp is OK once you've set it up; the problem is setting it up,
although I found FreeBSD ppp easier than Linux ppp. I set both up the
"hard way" ie. editing config files, as I find that in the long run
it's the "easy way".

> To Daniel - good luck!




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