Public Network (ISP)
		|
swtich/router
		|
firewall
		|
Private Network (LAN)


On the router (by the article):

ifconfig eth0 192.168.0.253 up
ifconfig eth1 192.168.0.254 up
echo "1" > /proc/sys/net/ipv4/ip_forward
echo "1" > /proc/sys/net/ipv4/conf/proxy_arp
route add -net 192.168.0.0/24 eth0
route add default eth1

On each client machine (by the article):

route add default gw 192.168.0.253 eth0
route add -net 192.168.0.0/24 eth0

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On the router (as I would use it):

ifconfig eth0 192.168.0.253 up
ifconfig eth0:1 192.168.0.254 up
echo "1" > /proc/sys/net/ipv4/ip_forward
echo "1" > /proc/sys/net/ipv4/conf/proxy_arp
route add -net 192.168.0.0/24 eth0
route add default eth0:1

On each client machine (as I would use it, not counting windows):

route add default gw 192.168.0.253 eth0
route add -net 192.168.0.0/24 eth0