Moxa UC-8416-T-LX [36/90] Nat example

UC-8410/8416/8418/8430 Managing Communication

4-9

NAT Example

The IP address of LAN1 is changed to 192.168.3.127 (you will need to load the module ipt_MASQUERADE):

#echo 1 > /proc/sys/net/ipv4/ip_forward

2. #modprobe ip_tables

3. #modprobe iptable_filter

4. #modprobe ip_conntrack

5. #modprobe iptable_nat

6. #modprobe ipt_MASQUERADE

7. #iptables -t nat –A POSTROUTING –o eth0 –j SNAT --to-source 192.168.3.127

#iptables –t nat –A POSTROUTING –o eth0 –j MASQUERADE

Enabling NAT at Bootup

In most real world situations, you will want to use a simple shell script to enable NAT when the

UC-8410/8416/8418/8430/8430 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=‘eth0’ #This is an external interface for setting up a valid IP address.

EXNET=‘192.168.4.0/24’ #This is an internal network address.

# Step 1. Insert modules.

# Here 2> /dev/null means the standard error messages will be dump to null device.

modprobe ip_tables 2> /dev/null

modprobe iptable_filter 2> /dev/null

modprobe iptable_nat 2> /dev/null

modprobe ip_conntrack 2> /dev/null

modprobe ip_conntrack_ftp 2> /dev/null

modprobe iptable_nat

modprobe ip_nat_ftp 2> /dev/null

# Step 2. Define variables, enable routing and erase default rules.

PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin