Julian's netowrking challenge 2005

[. at babolo.ru]

> Hi Julian,
> 
> > The challenge:
> > 
> > figure out a way so that all teh users on the network behind fxp0
> > hcan use the internet using the T1 attached to the cisco off fxp1
> > while all the advertised services (about 8 of them, few enough to
> > list by hand in rules etc.) which are also behind fxp0 but acccessed by 
> > NAT'd addresses from the addresses on fxp1's net are accessed soly via that 
> > T1.
> > 
> > [...]
> > 
> > I can get the 'forward' direction easily.. i.e. incoming packets.
> > 
> > It's the reverse direction that doesn't work for me.
> > I considerred running 2 NATDs
> > but I need to run ipfw to identify teh reverse streams to force back via 
> > fxp2
> > and the only way I can do that is by using the 'fwd' command.
> > if I do that I can't divert them and if I divert them to natd first, I can't
> > 'fwd' them afterwards as the NATing is already done for the other (wrong)
> > interface.
> 
> You definitely want a non-terminal "fwd" command.
> Ari Suutari has just implemented the "setnexthop" action that does the
> trick,
... or non-terminal "divert" command.

net.inet.ip.fw.one_pass=1

natd -i PORTI1 -o PORTO1 -a NAT1ADDR
natd -i PORTI2 -o PORTO2 -a NAT2ADDR

divert PORTO1 ip from server to any out fxp1
divert PORTO1 ip from server2 to any out fxp1
...
fwd ... ip from NAT1ADDR  to any out fxp1
divert PORTO2 ip from 192.168... to any out fxp1