ip masqurade

ip masqurade

[Gary Metcalf]

I'm running Slackware 8.1 with kernel 2.4.18. I'm needing to have some 
computers on my LAN to gateway to the internet via my Linux Modem. My 
modem does connect to the internet ok and I can use it via my Linux 
system. What I don't know and have been reading the How-To's is how to 
set this thing up. I've un-remarked some lines in my rc.modules file 
that is supose to allow ipmasqurade when I boot. Now I have learned that 
I need to build some tables and this is where I get lost.
    My Linux IP address is: 192.168.168.1   and one of my computers 
(windows) on my lan is: 192.168.168.2
What lines do I need to input for iptables to set this up where it will 
allow browsing and mail for my windows computer and other computers on 
my lan which will fall in the ip range of 192.168.168.0/24
     Gary

ip masqurade

[Gary Metcalf]

I'm running Slackware 8.1 with kernel 2.4.18. I'm needing to have some 
computers on my LAN to gateway to the internet via my Linux Modem. My 
modem does connect to the internet ok and I can use it via my Linux 
system. What I don't know and have been reading the How-To's is how to 
set this thing up. I've un-remarked some lines in my rc.modules file 
that is supose to allow ipmasqurade when I boot. Now I have learned that 
I need to build some tables and this is where I get lost.
   My Linux IP address is: 192.168.168.1   and one of my computers 
(windows) on my lan is: 192.168.168.2
What lines do I need to input for iptables to set this up where it will 
allow browsing and mail for my windows computer and other computers on 
my lan which will fall in the ip range of 192.168.168.0/24. I've set up 
my windows to use Gateway to my linux ip.
    Gary

RE: ip masqurade

[Rob Sterenborg]

> computers on my LAN to gateway to the internet via my Linux Modem. My 

You use a modem, so I guess you have aa ppp internet interface and a
dynamic IP address.
That's why we'll be using MASQUERADE. Otherwise use SNAT.

> my lan which will fall in the ip range of 192.168.168.0/24. 

# First disable forwarding so that nothing will happen before your rules
are set.
echo 0 > /proc/sys/net/ipv4/ip_forward

# Forward packets coming from your LAN to internet, DROP everything
else.
# When not specifying a table, the filter table is assumed.
iptables -P FORWARD DROP
iptables -A FORWARD -i <if_lan> -o <if_inet> -s 192.168.168.0/24 -j
ACCEPT
iptables -t nat -A POSTROUTING -o <if_inet> -s 192.168.168.0/24 -j
MASQUERADE 

# Enable forwarding.
echo 1 > /proc/sys/net/ipv4/ip_forward


Gr,
Rob