One-to-one NAT

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Revision as of 16:22, 20 March 2009 by Soulstace (Talk | contribs)
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One-to-one NAT (aka Static NAT) is a way to make systems behind a firewall and configured with private IP addresses (those addresses reserved for private use in RFC 1918) appear to have public IP addresses.¹

I'm using this type of setup, with three public IPs. WRT54GL v.1.1 with DD-WRT RC6 and it works just fine.²

I have done following:




set up new public static ip on dd-wrt wan interface vlan1

ifconfig vlan1:1 PUBLIC_IP netmask NETMASK broadcast BROADCAST 



route all packets for the new public ip, to a certain local ip

iptables -t nat -I PREROUTING -i vlan1 -d PUBLIC_IP -j DNAT --to-destination LAN_IP

masquerade returned packets from the local ip to the public ip

iptables -t nat -I POSTROUTING -o vlan1 -s LAN_IP -j SNAT --to-source PUBLIC_IP

forward port X to above local IP

iptables -I FORWARD -p tcp -i vlan1 -d LAN_IP --dport X -j ACCEPT

You could also replace above rule with the following:

iptables -I FORWARD -p all -i vlan1 -d LAN_IP -j ACCEPT 

which instead of forwarding just a single port, will let through all tcp/udp connections on all ports to this public ip-->lan ip.

With other words, no firewalling what so ever.