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NAT Forwarding Issue Endian and Vyatta Firewall

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Special Forums IP Networking NAT Forwarding Issue Endian and Vyatta Firewall
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Old 06-30-2010
NAT Forwarding Issue Endian and Vyatta Firewall
I've experienced this same issue with both the Endian Firewall Appliance and a Vyatta Firewall Appliance. Conversely, it works with a Draytek Firewall/Router.

I am trying to forward port 80 traffic to my internal web server which is located on the /24 subnet. I have an external static IP which is on the /29 subnet. I'm relatively well versed in firewalls so I proceeded to set up a DNAT rule to forward from the uplink to the internal server. I also set up firewall rules to allow port 80 into the internal network.

Unfortunately, the DNAT rule is not working as planned. I monitored the connections in the status section of the Endian system and I can see that the DNAT properly directs the packets but they end up being destroyed in the SYN_SENT state. In other words, the TCP packets are not getting a "handshake" (SYN/ACK) from the internal web server. This is also the same with a separate mail server operating on port 443.

Am I missing something simple here? I am currently using a Draytek router in production and it forwards all the ports without issue.

Thanks in advance for you help...
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LEARN ABOUT REDHAT

tc-fw

Firewall mark classifier in tc(8)				       Linux					 Firewall mark classifier in tc(8)

NAME

       fw - fwmark traffic control filter

SYNOPSIS

       tc filter ... fw [ classid CLASSID ] [ action ACTION_SPEC ]

DESCRIPTION

       the fw filter allows to classify packets based on a previously set fwmark by iptables.  If it is identical to the filter's handle, the fil-
       ter matches.  iptables allows to mark single packets with the MARK target, or whole connections using CONNMARK.	The benefit of using  this
       filter  instead of doing the heavy-lifting with tc itself is that on one hand it might be convenient to keep packet filtering and classifi-
       cation in one place, possibly having to match a packet just once, and on the other users familiar with iptables but not tc will have a less
       hard time adding QoS to their setups.

OPTIONS

       classid CLASSID
	      Push matching packets to the class identified by CLASSID.

       action ACTION_SPEC
	      Apply an action from the generic actions framework on matching packets.

EXAMPLES

       Take e.g. the following tc filter statement:

	      tc filter add ... handle 6 fw classid 1:1

       will match if the packet's fwmark value is 6.  This is a sample iptables statement marking packets coming in on eth0:

	      iptables -t mangle -A PREROUTING -i eth0 -j MARK --set-mark 6

SEE ALSO

       tc(8), iptables(8), iptables-extensions(8)

iproute2							    21 Oct 2015 				 Firewall mark classifier in tc(8)