[CentOS] Setting up a simple NAT on CentOS 3.5

[Bryan J. Smith]

Robert Moskowitz <rgm at htt-consult.com> wrote:
> Well I think this system is back on 3.5.  How do I tell? 
> Have not used it in a while...

cat /etc/redhat-release

> I need a NAT for some quick testing and this box was
> available.  Only a 6gb drive, so I can't install Astaro
> (which I have licenses for).
> So is there a simple way to turn on NATing?  Should I
> upgrade to 4.2?

Why would you upgrade to 4.2?  NetFilter and the IPTables
interface has changed little since 2.4.

E.g., given a private network of 172.31/16, and an
Internet-face interface of eth2

  /sbin/iptables -A POSTROUTING -t nat -s
172.31.0.0/255.255.0.0 -o eth2 -j MASQUERADE
  echo "1" >> /proc/sys/net/ipv4/ip_forward

This also assumes you already have existing iptables rules
regarding ESTABLISHED,RELATED states and other firewall
rules.

> This box is behind a firewall, so security risks are not
> the issue.  This time.

Is your firewall also doing NAT+PAT?  If so, then I don't
recommend 2 layers of NAT+PAT -- especially not on a
corporate network.



-- 
Bryan J. Smith  b.j.smith at ieee.org http://thebs413.blogspot.com
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