Moxa W325A-LX [45/74] Nat example

W315A/325A Linux User's Manual Managing Communications

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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 the LAN is changed to 192.168.3.127 (you will need to load the module ipt_MASQUERADE):

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

#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

8. #iptables –t nat –A POSTROUTING –o eth0 –s 192.168.3.0/24 –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 W315A/325A

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 ip_conntrack 2> /dev/null

modprobe ip_conntrack_ftp 2> /dev/null

modprobe ip_conntrack_irc 2> /dev/null

modprobe iptable_nat 2> /dev/null

modprobe ip_nat_ftp 2> /dev/null

modprobe ip_nat_irc 2> /dev/null