NATing in linux

immortaltechnique · 03-22-2007, 11:29 AM

Hi all i want to do away with a hardware firewall and i have the option of implementing NAT on my linux box.
I have 1 interface with a public ip and its default gateway is the router. I want to use the other interface as as the default gateway for the entire lan.
My question is since i have several domains with different ips how do i implement NATing or should i use Ip-Tables?

ramram29 · 03-22-2007, 12:05 PM

Do you mean that you are going to replace your router with your Linux computer? You can use multiptle IP addresses per device.

mether · 03-22-2007, 01:04 PM

Adding multiple rules for nat is no harm. If u have multiple IPs then u can make a range of IPs. But if u have multiple subnets then add multiple rules. Simple IP forwarding can also help if you have only single domain.

immortaltechnique · 03-23-2007, 01:09 AM

OK i do have a router but the thing is i have multiple subnets with different ips ie 172.x.x.x and 192.x.x.x My other idea was to use one interface on my linux server to NAT all the private ips to the second interface with a Public ip which is facing the internet: a 212.x.x.x

At the same time i have a web and mail server which will not be visible from the internet. So the alternative is to use the firewall which i really want to get rid of. Yes i can implement the linux firewall but my issue is with Nating

acid_kewpie · 03-24-2007, 08:38 AM

not really sure what you want to achieve here. at a simple routing level, you can put both 192.168.0.0/24 and 172.16.0.0/24 on the same physical nic if you wish to, nothing wrong with that. if you then have a number of public ip addresses being routed towards you, it's a simple iptable rule to nat each public ip to a matching private one if that's required.

note though that you don't need multiple mail servers and web servers (and therefore ip's) to host multiple domains.