Open up any text editor and put this in /etc/rc.d/rc.local
#Turn on IP forwarding echo 1 > /proc/sys/net/ipv4/ip_forward /sbin/ipchains -P forward DENY /sbin/ipchains -A forward -s 10.0.0.0/255.255.255.0 -j MASQ #If you telnet a lot, this will stop your connections from timing out at inconvenient times. /sbin/ipchains -M -S 7200 10 60 # #Uncomment the next line if you are using dialup or do not have a static ip. #echo "1" > /proc/sys/net/ipv4/ip_dynaddr # #Uncomment these for special services. /sbin/insmod ip_masq_ftp /sbin/insmod ip_masq_irc /sbin/insmod ip_masq_raudio /sbin/insmod ip_masq_quake #/sbin/insmod ip_masq_cuseeme #/sbin/insmod ip_masq_vdolive
put this in /etc/rc.d/init.d/network or you can put it in /etc/rc.d/rc.local
# Setup Automatic IP spoof protector if [ -e /proc/sys/net/ipv4/conf/all/rp_filter ]; then echo -n "Setting up IP spoofing protection..." for f in /proc/sys/net/ipv4/conf/*/rp_filter; do echo 1 > $f done echo "done." else echo PROBLEMS SETTING UP IP SPOOFING PROTECTION. BE WORRIED. echo "CONTROL-D will exit from this shell and continue system start up." echo # Start a single user shell on the console /sbin/sulogin $CONSOLE fi
You will need 2 nics for your gateway. The first nic (eth0) will be connected to the internet. The second (eth1) will be on your local intranet. Make eth1 have the IP address of 10.0.0.2 and a netmask of 255.255.255.0. Make the other machines on your local net have the ip address of 10.0.0.[3-254] and a netmask of 255.255.255.0. Once that has been done and all the machines are connected, they should be able to "talk" to each other.
Now you need to set the machines on the local net to forward packets to the gateway when they want to use an ip address not within the local net. To do that you will need to add the gateway's IP address in the gateway tab for windows, for a linux box type "route add default gw