One-to-one NAT
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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. | + | ==Introduction== |
+ | 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. | ||
- | These examples have been tested and work with multiple public static IPs. | ||
- | Tested with: | ||
- | * WRT54GL v.1.1 with DD-WRT RC6 and it works just fine.² | ||
- | * DD-WRT v24-sp2 (01/01/09) mega on Linksys WRT 600N V1 | ||
- | __TOC__ | ||
==Setup== | ==Setup== | ||
- | |||
Begin by setting your WAN to use one of the static addresses using the web ui and then use these scripts to add the rest. Everything in square brackets needs to be replaced by your values. Examples are at the bottom. | Begin by setting your WAN to use one of the static addresses using the web ui and then use these scripts to add the rest. Everything in square brackets needs to be replaced by your values. Examples are at the bottom. | ||
- | ====Startup==== | ||
- | Set up new public static IP on dd-wrt WAN interface. This must be done for each public static IP and should be saved to the Startup script using the Save Startup button on the Administration -> Commands page. If you do not know how to calculate your broadcast address, then enter your WAN IP and subnet mask into this [[http://www.subnet-calculator.com/ calculator]]. | ||
- | If | + | ===Startup=== |
- | WANIF=` | + | Set up new public static IP on dd-wrt WAN interface. This must be done for each public static IP and should be saved to the Startup script using the Save Startup button on the Administration -> Commands page. If you do not know how to calculate your broadcast address, then enter your IP and subnet mask into this [[http://www.subnet-calculator.com/ calculator]]. |
- | + | ||
- | ifconfig $WANIF:1 [PUBLIC_IP1] netmask | + | WANIF=`get_wanface` |
- | ifconfig $WANIF:2 [PUBLIC_IP2] netmask | + | ifconfig $WANIF:1 [PUBLIC_IP1] netmask [NETMASK] broadcast [BROADCAST] |
- | ifconfig $WANIF:3 [PUBLIC_IP3] netmask | + | ifconfig $WANIF:2 [PUBLIC_IP2] netmask [NETMASK] broadcast [BROADCAST] |
+ | ifconfig $WANIF:3 [PUBLIC_IP3] netmask [NETMASK] broadcast [BROADCAST] | ||
- | + | ===Firewall=== | |
Here are some examples of firewall rules to NAT the external IP's to your internal IP's. Put them in the command box and use the Save Firewall button on the Administration -> Commands page to save them to your firewall script. | Here are some examples of firewall rules to NAT the external IP's to your internal IP's. Put them in the command box and use the Save Firewall button on the Administration -> Commands page to save them to your firewall script. | ||
- | + | ====SNAT/DNAT==== | |
Route all packets for the new public IP, to a certain local IP. | Route all packets for the new public IP, to a certain local IP. | ||
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iptables -t nat -I POSTROUTING -s [LAN_IP] -j SNAT --to-source [PUBLIC_IP] | iptables -t nat -I POSTROUTING -s [LAN_IP] -j SNAT --to-source [PUBLIC_IP] | ||
- | + | ====PORT FORWARD==== | |
Forward port X to above local IP | Forward port X to above local IP | ||
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===Startup Script=== | ===Startup Script=== | ||
# Save Startup | # Save Startup | ||
- | WANIF=` | + | WANIF=`get_wanface` |
- | + | ifconfig $WANIF:1 173.X.X.250 netmask [NETMASK] broadcast [BROADCAST] | |
- | ifconfig $WANIF:1 173.X.X.250 netmask | + | ifconfig $WANIF:2 173.X.X.251 netmask [NETMASK] broadcast [BROADCAST] |
- | ifconfig $WANIF:2 173.X.X.251 netmask | + | ifconfig $WANIF:3 173.X.X.252 netmask [NETMASK] broadcast [BROADCAST] |
- | ifconfig $WANIF:3 173.X.X.252 netmask | + | |
===Firewall Script=== | ===Firewall Script=== | ||
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==Resources== | ==Resources== | ||
- | + | http://www.shorewall.net/NAT.htm<br> | |
- | + | http://www.dd-wrt.com/phpBB2/viewtopic.php?t=24555<br> | |
http://www.dd-wrt.com/phpBB2/viewtopic.php?p=400472#400472 | http://www.dd-wrt.com/phpBB2/viewtopic.php?p=400472#400472 | ||
Revision as of 02:35, 24 January 2011
Contents |
Introduction
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.
Setup
Begin by setting your WAN to use one of the static addresses using the web ui and then use these scripts to add the rest. Everything in square brackets needs to be replaced by your values. Examples are at the bottom.
Startup
Set up new public static IP on dd-wrt WAN interface. This must be done for each public static IP and should be saved to the Startup script using the Save Startup button on the Administration -> Commands page. If you do not know how to calculate your broadcast address, then enter your IP and subnet mask into this [calculator].
WANIF=`get_wanface` ifconfig $WANIF:1 [PUBLIC_IP1] netmask [NETMASK] broadcast [BROADCAST] ifconfig $WANIF:2 [PUBLIC_IP2] netmask [NETMASK] broadcast [BROADCAST] ifconfig $WANIF:3 [PUBLIC_IP3] netmask [NETMASK] broadcast [BROADCAST]
Firewall
Here are some examples of firewall rules to NAT the external IP's to your internal IP's. Put them in the command box and use the Save Firewall button on the Administration -> Commands page to save them to your firewall script.
SNAT/DNAT
Route all packets for the new public IP, to a certain local IP.
iptables -t nat -I PREROUTING -d [PUBLIC_IP] -j DNAT --to-destination [LAN_IP]
Route packets on a port on the new public IP, to a different port of a local IP. Note that you can skip [LAN_Port] if it matches [Destination_Port].
iptables -t nat -I PREROUTING -d [PUBLIC_IP] -p tcp --dport [Destination_Port] -j DNAT --to-destination [LAN_IP]:[LAN_Port]
Masquerade returned packets from the local ip to the public IP
iptables -t nat -I POSTROUTING -s [LAN_IP] -j SNAT --to-source [PUBLIC_IP]
PORT FORWARD
Forward port X to above local IP
iptables -I FORWARD -d [LAN_IP] -p tcp --dport [Destination_Port] -j ACCEPT
You could also replace above rule(s) with the following:
iptables -I FORWARD -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.
In other words, forwarding all connections would be no firewalling for that IP address.
Copy/Paste Examples
Startup Script
# Save Startup WANIF=`get_wanface` ifconfig $WANIF:1 173.X.X.250 netmask [NETMASK] broadcast [BROADCAST] ifconfig $WANIF:2 173.X.X.251 netmask [NETMASK] broadcast [BROADCAST] ifconfig $WANIF:3 173.X.X.252 netmask [NETMASK] broadcast [BROADCAST]
Firewall Script
# Save Firewall # WAN .250 -> LAN .15 iptables -t nat -I PREROUTING -d 173.X.X.250 -j DNAT --to 192.168.0.15 iptables -t nat -I POSTROUTING -s 192.168.0.15 -j SNAT --to 173.X.X.250 iptables -I FORWARD -d 192.168.0.15 -p tcp --dport 21 -j ACCEPT iptables -I FORWARD -d 192.168.0.15 -p tcp --dport 80 -j ACCEPT iptables -I FORWARD -d 192.168.0.15 -p tcp --dport 5900 -j ACCEPT # WAN .251 -> LAN .20 iptables -t nat -I PREROUTING -d 173.X.X.251 -j DNAT --to 192.168.0.20 iptables -t nat -I POSTROUTING -s 192.168.0.20 -j SNAT --to 173.X.X.251 iptables -I FORWARD -d 192.168.0.20 -p tcp --dport 21 -j ACCEPT iptables -I FORWARD -d 192.168.0.20 -p tcp --dport 80 -j ACCEPT iptables -I FORWARD -d 192.168.0.20 -p tcp --dport 5900 -j ACCEPT
Resources
http://www.shorewall.net/NAT.htm
http://www.dd-wrt.com/phpBB2/viewtopic.php?t=24555
http://www.dd-wrt.com/phpBB2/viewtopic.php?p=400472#400472