Red Hat Bugzilla – Bug 99031
iptables NAT chain not working with DNAT and SNAT
Last modified: 2007-04-18 12:55:38 EDT
From Bugzilla Helper: User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.2.1) Gecko/20030225 Description of problem: Redhat 9 with all patches applied from RHN. Start IPtables with default settings (ACCEPT all) using /etc/init.d/iptables start. Set rule iptables -t nat -A POSTROUTING -o eth0 -p tcp -j SNAT --to-source 172.20.0.248 Ran ethereal to see network traffic and it kept the source as my private ip of 192.168.1.101 rather than changing it to 172.20.0.248. Yes my ip_forward is set to 1 in the proc filesystem. I have tried the exact same steps using Knoppix boot disk and it works fine. Version-Release number of selected component (if applicable): iptables-1.2.7a-2 How reproducible: Always Steps to Reproduce: 1.in description 2. 3. Additional info: Not good when you have firewall rules that worked before then you perform an upgrade and your firewall has holes in it now...
I have tested this with different kernel and iptables versions and it works for me: kernel-2.4.20-9 to kernel 2.4.20-18.9 iptables-1.2.7a-2 to iptables-1.2.8-7 I have used tcpdump on 3 machines: source host, mangle host, destination host. Please check this again.
no response from reporter - please reopen this bug if you are able to reproduce the problem.
I was having similar problems with kernel-2.4.20-20.9 and iptables-1.2.7a-2 -- rules in the nat table didn't seem to work. Upgrading to iptables-1.2.8-9.1 seems to solve the problem.