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Old 08-26-2008, 06:21 PM   #1
mikanoot
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Registered: Aug 2008
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NAT Troubleshooting


How could I troubleshoot my NAT setup. I have 2 computers.


comp1: 192.168.0.3 (eth1) and dhcp for (eth0)
comp2: 192.168.0.1 (eth0)

I have enabled ip_forwarding and my firewall is as follows.
Code:
iptables -P INPUT DROP
iptables -P FORWARD ACCEPT

iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT

iptables -A INPUT -s 127.0.0.0/8 -d 127.0.0.0/8 -i lo -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -i eth1 -j ACCEPT
iptables -A INPUT -p icmp -j ACCEPT

iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
iptables -A FORWARD -i eth0 -o eth1 -m state --state RELATED,ESTABLISHED -j ACCE
PT
iptables -A FORWARD -i eth1 -o eth0 -j ACCEPT
I stll can not connect from the second computer. I can access my apache webserver from the second computer, but not the internet.
What steps can I take to troubleshoot this if anyone knows.
 
Old 08-26-2008, 06:31 PM   #2
jschiwal
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Registered: Aug 2001
Location: Fargo, ND
Distribution: SuSE AMD64
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This weblog page may help.
http://linuxadministration.wordpress...-masquerading/

Make sure to pay attention to which kernel modules you need loaded. For example, you may need nf_conntrack loaded.
Make sure that ip_forward is enabled. Check that the gateway and resolv.conf values on the second computer are correct.

I noticed a few months back the some of the kernel modules have new names. On the most recent kernels the modules probably begin with nf_.
 
  


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