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Old 10-25-2005, 06:17 AM   #1
Zorrocaesar
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Registered: Oct 2005
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Problem with Port Forwarding


I am using Slackware 10.2 with a 2.4 kernel for NAT and a WIN XP SP2 workstation which runs a DC client.
My iptables configuration looks something like this:

Code:
#Enable Forward
iptables -A FORWARD -i $EXTIF -o $INTIF -m state ESTABLISHED,RELATED -j ACCEPT
iptables -A FORWARD -i $INTIF -o $EXTIF -j ACCEPT

# NAT
iptables -t nat -A POSTROUTING-o $EXTIF -J SNAT --to 82.77.115.78

#Port Forwarding
iptables -t nat -A PREROUTING -d 82.77.115.78 -p tcp --dport 6783 -j DNAT --to-destination 192.168.0.2
iptables -t nat -A PREROUTING -d 82.77.115.78 -p udp --dport 5758 -j DNAT --to-destination 192.168.0.2

The DC client is configured as follows:
Firewall with manual port forwarding
TCP port: 6783
UDP port: 5758
External/WAN IP: 82.77.115.78


The NAT works without any problems, meaning that I can write this text from the Win dows workstation.
Unfortunatey, the port forwarding part is not working meaning that even if I set the above ports (6783 - TCP, 5758 - UDP), the DC client doesn't have any traffic on these ports. It works well when it's active with a real IP or when passive through the NAT server.
As far as I know, this whole configuration should work. What am I doing wrong?
 
Old 10-25-2005, 07:18 AM   #2
uberNUT69
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Registered: Jan 2005
Location: Tasmania
Distribution: Xen Debian Lenny/Sid
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Have you checked
# cat /proc/sys/net/ipv4/ip_forward

it needs to be set to 1 for forwarding:
eg.
# echo 1 > /proc/sys/net/ipv4/ip_forward
 
  


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