> 
> OK, I found pppd and downloaded it. I have a little scenario that I'd 
> like to know if it is possible:
> 
> I have two Macs (the Performa 600 and the IIsi, the IIsi running NetBSD). 
> They are connected via printer port to each other.

With a printer cable, yes? Printer cables have null modems wired in.
If serial terminals on each end talk to each other (under MacOS or
whatever), you're set.

> Now, I (unfortunately) only have 1 modem. What I'm asking is:
> 
> Could I hook this modem up to the IIsi, then dial up my ISP and connect 
> using pppd, then use a PPP server on the IIsi, and allow my Performa 600 
> to connect via the printer cable and MacTCP and MacPPP to the IIsi?

Yes. Someone's done it (and I thought wrote a FAQ/How-To). Basically
you either get two IP addresses from your ISP and have the second
routed through your IIsi, or you run software which takes all connections
made by the Performa and makes them look like they came from the IIsi.

> The only thing I am having problems understanding is how to simulate a 
> TCP network between the Performa and IIsi.

Why simulate one? Use a real one; this is UNIX after all. :-)
I.E. ppp under MacOS set up for a direct connection.

> If this is possible, could someone recommend a nice PPP server?

What's wrong with pppd? pppd is a symmetric protocall; the server is
the client is the server.

I have gotten my IIsi and my SE/30 both running NetBSD, and I fire pppd
up on both ports of my IIsi, one to my ISP and the other to the SE/30.
I am able to telnet to the IIsi from the SE/30, and then on to the world.
But the SE/30's mostly just so I can test unix-to-unix connections.
Since there's only one of me, and I'd rather web-surf from the IIsi, I
don't do any sort of MacOS ppp work, or IP forwarding.

Basically I made up two new IP addresses, 126.0.0.1 and 126.0.0.2.
pppd's setup for the printer port on the IIsi knows that it's
address os 126.0.0.2, and it connects to 126.0.0.1. The SE/30
just fires up w/o a connect script, and will learn its address from
the IIsi (just as the IIsi learns its modem address from the ISP).
The SE/30 ends up with a route of 126.0.0.1 to localhost, 126.0.0.2
to 126.0.0.1, and 126.0.0.2 as default. The IIsi knows the printer
port is 126.0.0.2 (routed to localhost), and 126.0.0.1 routes through
126.0.0.2. The IIsi's /etc/hosts knows 126.0.0.1 is "banana" and
126.0.0.2 is pokey-side-door. As I said, I don't have any IP
forwarding or routed fired up, so noone outside my house
knows about the 126.X.X.X addresses (and 126.X.X.X was allotted,
as I recall, for direct-connected NFS servers; when you have the
regular net, and an NFS-only ethernet).

Hope this helps.

Take care,

Bill