Ubuntu Networking :: How To Use IPtables For Different NAT Implementation

IPtables, implementing each type of NAT
-Full Cone NAT
-Restricted Cone NAT
-Port Restricted Cone NAT
-Symmetric NAT
using IPTables.

Explanation:
Full Cone: A full cone NAT is one where all requests from the same internal IP address and port are mapped to the same external IP address and port. Furthermore, any external host can send a packet to the internal host, by sending a packet to the mapped external address.

Restricted Cone: A restricted cone NAT is one where all requests from the same internal IP address and port are mapped to the same external IP address and port. Unlike a full cone NAT, an external host (with IP address X) can send a packet to the internal host only if the internal host had previously sent a packet to IP address X.

Port Restricted Cone: A port restricted cone NAT is like a restricted cone NAT, but the restriction includes port numbers. Specifically, an external host can send a packet, with source IP address X and source port P, to the internal host only if the internal host had previously sent a packet to IP address X and port P.

Symmetric: A symmetric NAT is one where all requests from the same internal IP address and port, to a specific destination IP address and port, are mapped to the same external IP address and port. If the same host sends a packet with the same source address and port, but to a different destination, a different mapping is used. Furthermore, only the external host that receives a packet can send a UDP packet back to the internal host.

On the netfilter mailinglist, Pedro Goncalves suggested the following:
192.168.2.170 is "public" address and 10.0.0.1 is "private" address

/-"Full Cone NAT", with the following rules:/

HTML Code:
iptables -t nat -A POSTROUTING -o eth0 -j SNAT --to-source 192.168.2.170
iptables -t nat -A PREROUTING -i eth0 -j DNAT --to-destination 10.0.0.1

/-"Port Restricted Cone NAT", with just a single rule:/

HTML Code:
iptables -t nat -A POSTROUTING -o eth0 -j SNAT --to-source 192.168.2.170