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9.3

iptables / routing issues :(

Asked by lojikop in Linux Networking, Network Software Firewalls, Unix Networking

I have a CentOS box with 2 interfaces eth0 and eth1.

eth0 is connected directly to the ISP, eth1 is connected to the LAN. eth1 also could have Internet access but its behind NAT.

Anyway, I wanted to restrict all incoming access on eth0 to only some specific IPs, Subnets etc. I take the INPUT chain and make it pass through my custom FIREWALL chain. I ALLOW my required subnet and IPs, including a DNS server, but then my last rule in the FIREWALL chain is :"-i eth0 -j DROP". So literally anything incoming from eth0 besides the allowed list gets dropped, period.

Problem is that cuts my internet access (except for NS lookup, which only works because I have a DNS server added to the ALLOWED list).

I would like iptables to allow traffic coming back in eth0, IF and ONLY IF it has been started/initialized by the box. As of right now traffic going to the default gw (which is on eth0) goes out, but of course on the way back in it gets dropped.

That would be the ideal solution, otherwise, how can I direct internet traffic to eth1 without getting too carried away with the routing table for eth0.

 
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Keywords: iptables / routing issues :(
 
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[+][-]05/07/09 05:07 PM, ID: 24331964Expert Comment

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[+][-]05/07/09 05:36 PM, ID: 24332089Accepted Solution

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About this solution

Zones: Linux Networking, Network Software Firewalls, Unix Networking
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Solution Provided By: KeremE
Participating Experts: 2
Solution Grade: A
 
 
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