problem with iptables nat II
because some people didn't understand
our problems, here again:
Wintel computer with actual sarge 2.6.8-2
and actual iptables,
three network interfaces
net one: 172.31.24.0/21
net two: 192.168.2.0/24
net one is the internal, net two the
dmz. net three the internet.
We like to do some double natting of
our dmz machines:
The (internal) IP of one dmz computer
may be 192.168.2.20
The IP from the intranet should be 172.31.27.20
The IP from the internet should be 22.214.171.124
Simple 1:1 static natting, but route
dependend. Easily done by iproute2.
No more longer possible because the
kernel was changed and nat by ip route/rule isn't possible anymore.
We got several manuals like NAT HOWTO
or iptables from LeRoy D. Cressy or double nat HOWTO.
Most of them deal with port forwarding
or masquerading. Nice, but this did not help.
NETMAP could be an possibility, but
Cressy points out that connection tracking didn't work well (whatever this
I googled NETMAP, but still now I didn't
find some real good advertisement about this.
And no, I'm not so good to take the
sources of iptable & patches and learn about all circumstances by miself,
In our test environment, this didn't
| # NAT
| iptables -t nat -A POSTROUTING -s 192.168.2.20 -o eth0 -j SNAT --to
| iptables -t nat -A PREROUTING -i eth1 -d 172.31.27.20 -j DNAT --to
Dr. Günter Sprakties