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Internal LAN and External ppp0 : webmin Firewall Routing


On "Networking - Linux Firewall" tab of webmin add the following :

Packet Filtering (filter) table (drop-down box at top of page) :

Forwarded packets (FORWARD) section :

Rule #1: Comment : #Forward stuff from eth0 Action: Accept if: incoming interface = eth0

Rule #2: Comment : #default Action: Run Chain RH-Firewall-1-INPUT if: (always)

Network Address Translation (nat) table (drop-down box at top of page) :

Packets after routing (POSTROUTING) section : Rule #1 : Comment : #Masquerade to ppp0 Action : Masquerade if: Outgoing interface = ppp0

Setting up LAN machines

From then, the LAN can be set up with hard IP addresses in the 192.168.1.x range. Default Gateway = address of SpeedHouse machine (, netmask of

Set the DNS address in /etc/resolv.conf on the LAN machines (connected to eth0) to the address(es) used by ppp0 (look for these in the /etc/resolv.conf on routing machine).

Switch on Forwarding

Temporary switch-on of forwarding (for testing) :

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

Permanent switch-on of forwarding, into the file /etc/sysconfig/network add the line :


Another method is to alter the Linux kernel config file: /etc/sysctl.conf. Set the following value:

net.ipv4.ip_forward = 1