NAT and PPTP

[Sten Daniel Sørsdal]

> FreeBSD makes a very good NAT router... for most applications.
> But a client of mine is having terrible trouble with it when
> trying to use NAT with one particular protocol: PPTP.
> 
> Here's what's going on. A client has a FreeBSD box that's serving as a
> NAT router. He has one public IP, and lots of PCs behind the router on
> unregistered IPs. This works fine when they're doing 
> browsing, etc., but
> fails horribly when users try to use PPTP to tunnel out into 
> another LAN
> across the Internet.
> 

natd handles pptp. we have multiple clients who are NATed and they connect
to different pptp gateways (occasionally the same too).

if you are running a poptop pptp server and you want multiple clients 
connecting to this one pptp server; make sure you get the GRE ID update
(poptop always sets the id to 0 - messes up two connections).

make sure you divert gre packets on their way out as well.

- sten