User`s manual
UC-7420/7410 User’s Manual Managing Communication
4-11
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.
# 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_nat_ftp 2> /dev/null
modprobe ip_nat_irc 2> /dev/null
modprobe ip_conntrack 2> /dev/null
modprobe ip_conntrack_ftp 2> /dev/null
modprobe ip_conntrack_irc 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
export PATH
echo “1” > /proc/sys/net/ipv4/ip_forward
/sbin/iptables -F
/sbin/iptables -X
/sbin/iptables -Z
/sbin/iptables -F -t nat
/sbin/iptables -X -t nat
/sbin/iptables -Z -t nat
/sbin/iptables -P INPUT ACCEPT
/sbin/iptables -P OUTPUT ACCEPT
/sbin/iptables -P FORWARD ACCEPT
/sbin/iptables -t nat -P PREROUTING ACCEPT
/sbin/iptables -t nat -P POSTROUTING ACCEPT
/sbin/iptables -t nat -P OUTPUT ACCEPT
# Step 3. Enable IP masquerade.
Dial-up Service—PPP
PPP (Point to Point Protocol) is used to run IP (Internet Protocol) and other network protocols over
a serial link. PPP can be used for direct serial connections (using a null-modem cable) over a
Telnet link, and links established using a modem over a telephone line.
Modem / PPP access is almost identical to connecting directly to a network through
UC-7420/7410’s Ethernet port. Since PPP is a peer-to-peer system, UC-7420/7410 can also use
PPP to link two networks (or a local network to the Internet) to create a Wide Area Network
(WAN).