Moxa Technologies UC-7420/7410 user manual NAT Example, Enabling NAT at Bootup

UC-7420/7410 User’s Manual Managing Communication

NAT

NAT (Network Address Translation) protocol translates IP addresses used on one network different IP addresses used on another network. One network is designated the inside network and the other is the outside network. Typically, UC-7420/7410 connects several devices on a network and maps local inside network addresses to one or more global outside IP addresses, and un-maps the global IP addresses on incoming packets back into local IP addresses.

NOTE Click on the following link for more information about iptables and NAT:

http://www.netfilter.org/documentation/HOWTO/NAT-HOWTO.html

NAT Example

The IP address of all packets leaving LAN1 are changed to 192.168.3.127 (you will need to load the module ipt_MASQUERADE):

IP/Netmask: 192.168.3.100/24

Gateway: 192.168.3.127

PC1 (Linux or Windows)

LAN1

LAN1:ixp0 192.168.3.127/24

UC-7420

LAN2:ixp1 192.168.4.127/24

LAN2

PC2 (Linux or Windows)

IP/Netmask: 192.168.4.100/24

Gateway: 192.168.4.127

NAT Area / Private IP

1.#ehco 1 > /proc/sys/net/ipv4/ip_forward

2.#modprobe iptable_nat

3.#modprobe ip_conntract

4.#modprobe ipt_MASQUERADE

5.#iptables -t nat –A POSTROUTING –o ixp0 –j SNAT --to-source 192.168.3.127

or

6.#iptables –t nat –A POSTROUTING –o ixp0 –j MASQUERADE

Enabling NAT at Bootup

In the most of real world situations, you will want to use a simple shell script to enable NAT when UC-7420/7410 boots up. The following script is an example.

#!/bin/bash

#If you put this shell script in the /home/nat.sh

#Remember to chmod 744 /home/nat.sh

#Edit the rc.local file to make this shell startup automatically.

#vi /etc/rc.d/rc.local

#Add a line in the end of rc.local /home/nat.sh

EXIF=‘ixp0’ #This is an external interface for setting up a valid IP address. EXNET=‘192.168.4.0/24’ #This is an internal network address.

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