[CentOS] Firewall frustration

[Steven Haigh]

On 02/01/2008, at 4:11 AM, Robert Moskowitz wrote:
> I spent much of the past 24 hours trying to find out how to set up  
> iptables for firewall routing WITHOUT NATing. Could not find anything.


*boggle* Is it really that hard?

## Clear up whatever is in there at the moment.
iptables -F INPUT
iptables -F FORWARD
iptables -F OUTPUT
iptables -t nat -F POSTROUTING

## Accept anything related to existing connections
iptables -A INPUT -i ppp0 -m state --state RELATED,ESTABLISHED -j ACCEPT
iptables -A FORWARD -i ppp0 -m state --state RELATED,ESTABLISHED -j  
ACCEPT

## I want to allow incoming port 80 to 1.2.3.4
iptables -A FORWARD -i ppp0 -d 1.2.3.4 -p tcp -m state --state NEW -m  
tcp --dport 80 -j ACCEPT

## I want to allow incoming port 123 (ntp) to 1.2.3.6
iptables -A FORWARD -i ppp0 -d 1.2.3.6 -p udp -m udp --dport 123 -j  
ACCEPT

## Lets block ALL other incoming things
iptables -A INPUT -j DROP
iptables -A FORWARD -j DROP

There you go. That's a very basic firewall using iptables in about 3  
minutes :)

--
Steven Haigh

Email: netwiz at crc.id.au
Web: http://www.crc.id.au
Phone: (03) 9001 6090 - 0412 935 897