verkot samalla ip:llä

http://lists.netfilter.org/pipermail/netfilter/2005-February/058777.html
  http://marc.info/?l=netfilter&m=110737820716813&w=2
  http://marc.info/?l=netfilter&m=110027573811157&w=2

http://www.netfilter.org/documentation/HOWTO/NAT-HOWTO-6.html
http://linux-ip.net/html/nat-dnat.html