Intenet Sharing on Linux

friendklay · 06-06-2005, 11:32 PM

Hi gurus,
how do I do a simple internet sharing on Linux? I know I have to use iptables and add some routes. I have two network cards. One connects to the ADSL Modem, while the other connects to the internal network. How do I set this up?
Thanks

~=gr3p=~ · 06-07-2005, 12:03 AM

Quote:

Originally posted by friendklay
Hi gurus,
how do I do a simple internet sharing on Linux? I know I have to use iptables and add some routes. I have two network cards. One connects to the ADSL Modem, while the other connects to the internal network. How do I set this up?
Thanks

very good document on using the best Squid proxy server :

http://www.linuxhomenetworking.com/linux-adv/squid.htm

aaa · 06-07-2005, 12:06 AM

Use this script:

Code:

EXTIF=adsl_interface_name_here
INTIF=internal_interface_name_here
iptables -t nat -A POSTROUTING -o $EXTIF -j MASQUERADE
iptables -A FORWARD -i $INTIF -j ACCEPT
echo 1 > /proc/sys/net/ipv4/ip_forward

Also you may want to setup dhcpd.

friendklay · 06-07-2005, 12:21 AM

Quote:

Originally posted by aaa
Use this script:

Code:

EXTIF=adsl_interface_name_here INTIF=internal_interface_name_here iptables -t nat -A POSTROUTING -o $EXTIF -j MASQUERADE iptables -A FORWARD -i $INTIF -j ACCEPT echo 1 > /proc/sys/net/ipv4/ip_forward

Also you may want to setup dhcpd.

So the gateway IP for the INTIF would be the IP address of EXTIF, and the gateway IP of the machines inside the LAN would be the IP of INTIF, right?

lindani · 06-07-2005, 08:41 AM

Hi friendklay :

your adsl interface=ppp0

you must write this command only:

iptables -t nat -A POSTROUTING -o ppp0 -j MASQUERADE

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

at end add this line(echo 1 >/proc/sys/net/ipv4/ip_forward) to /etc/rc.d/rc.local file.

good luck.

friendklay · 06-08-2005, 05:08 AM

Quote:

Originally posted by lindani
Hi friendklay :

your adsl interface=ppp0

you must write this command only:

iptables -t nat -A POSTROUTING -o ppp0 -j MASQUERADE

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

at end add this line(echo 1 >/proc/sys/net/ipv4/ip_forward) to /etc/rc.d/rc.local file.

good luck.

My adsl interface is eth0, since I am using an ADSL Modem/Router combo box. I also have two network cards, to seperate my internal network and the internet. I have got it all working now. However, I can't access my adsl console anymore, nor can I ping out. What's amiss?

friendklay · 06-08-2005, 06:48 AM

Quote:

Originally posted by aaa
Use this script:

Code:

EXTIF=adsl_interface_name_here INTIF=internal_interface_name_here iptables -t nat -A POSTROUTING -o $EXTIF -j MASQUERADE iptables -A FORWARD -i $INTIF -j ACCEPT echo 1 > /proc/sys/net/ipv4/ip_forward

Also you may want to setup dhcpd.

I have got that part done. How do I setup gateway IPs for the two interfaces? The thing is I thought to put the IP of eth0 as the gateway IP of eth1. But this didn't work. It seems it only works when I leave the gateway IP of eth1 blank.

aaa · 06-08-2005, 12:04 PM

Why do you need gateway ips? eth0 should get it's gateway from the adsl automatically, the eth1 does not need one. You only need to assign the gateway on the second computer.