Hi,
On Thu, Nov 26, 2009 at 1:17 AM, Tait Clarridge tait@clarridge.ca wrote:
peter.peltonen@gmail.com wrote:
Hi,
I am unable to get my LAN masqueraded using SNAT with CentOS 5.3 and iptables.
I have the following setup:
eth0: connects to internet with static public IP 1.2.3.1 (obscured here for privacy) eth1: connects to DMZ with static public IP 1.2.3.2 (obscured here for privacy) eth2: connects to LAN with static private IP 192.168.0.1
Traffic to hosts in the DMZ/Internet through eth0/1 work fine.
I had to get the VPN address range masqueraded on the LAN as the gateway address.. so for example:
VPN Server LAN IP: 192.168.1.20 (not the real thing, but doesn't matter) VPN IP Range: 10.99.0.0
So when I connect through OpenVPN, my tunnel adaptor is given an ip like 10.99.0.5 (basically like a LAN, or your eth2).
What I did in IPTABLES is the following (eth0 is the LAN connection for the VPN server)
iptables -t nat -A POSTROUTING -s 10.99.0.0/255.255.255.0 -o eth0 -j MASQUERADE
After that it worked. All connections to anything on the LAN appear as if I am coming from 192.168.1.20. Just make sure that forwarding is enabled (I believe it is required for masquerade):
cat /proc/sys/net/ipv4/ip_forward
If it equals 0, change it to 1.
You may want to remove all the other entries you tried to get LAN->Internet going to ensure there is nothing conflicting.
It appears my problems were somehow DNS related: I can't access my ISPs DNS from LAN when masquerading is on (I can't understand why). Using a nameserver in the DMZ solved my issues and everything seems to work now ok.
Thanks for your help, Peter