Internal LAN and External ppp0 : webmin Firewall Routing

December 30, 2006
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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 (192.168.1.254), netmask of 255.255.255.0

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 :

FORWARD_IPV4=true

Another method is to alter the Linux kernel config file:

/etc/sysctl.conf

. Set the following value:

net.ipv4.ip_forward = 1

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