[pptp-server] All good except for data transfer?

[Chris Swan]

I'm using ppp-2.3.8 (plus the mppe patch and SSL), the newest PoPToP,
and linux kernel 2.2.12.  Clients connect OK, and everything _seems_
peachy keen.  However, clients only seem to be able to ping/contact
the host--no data seems to be able to get between any of the
clients...they can't even ping each other.

When each client connects a different PPP device is created--urm,
doesn't that mean that bridging would need to be enabled to get data
between the two different devices?  Are there other kernel options I'm
missing?  Does forwarding need to be enabled?  GRE forwarding?

All of the clients are getting assigned IP addresses in the same
subnet (192.168.2.*), and the host IPs are also in the same Class C.
This be friggin' frustrating!

There is no firewalling set up on the server at all--so I didn't think
I needed to play with ipfwadm, or ipchains.  Do I? Do I need to play
with NAT if I'm not using any firewalling?

The howto mentions how to set up an ip-up file to answer the proxyarp
requests, and after doing so there are no more proxyarp errors in the
log file (but the arp tables sure look funny--I wish the howto would
show what the arp tables _should_ look like after doing it.)  The only
errors in my logs anymore look like this:

Sep  2 10:36:40 rosebud pppd[3847]: CCP: timeout sending
Config-Requests