Firewall

NOTE: If you run SuSE Linux, try this HowTo first.

If you set TCP port in aMule to XX and UDP port to YY then you have to set your firewall like this:

iptables -A INPUT -p tcp --dport XX -j ACCEPT
iptables -A INPUT -p udp --dport XX+3 -j ACCEPT
iptables -A INPUT -p udp --dport YY -j ACCEPT

If you want to setup aMule behind a NAT gateway, you should add these lines to your iptables configuration script, on the gateway :

EXTIF is your external interface

EMULEPORT=4662
EMULEUDP=4672
EMULEUDP2=`expr $EMULEPORT + 3`
EMULEHOST=10.0.0.2
iptables -t nat -A PREROUTING -i $EXTIF -p tcp --destination-port $EMULEPORT -j DNAT --to-destination $EMULEHOST:$EMULEPORT
iptables -t nat -A PREROUTING -i $EXTIF -p udp --destination-port $EMULEUDP -j DNAT --to-destination $EMULEHOST:$EMULEUDP
iptables -t nat -A PREROUTING -i $EXTIF -p udp --destination-port $EMULEUDP2 -j DNAT --to-destination $EMULEHOST:$EMULEUDP2

You also should make sure that your FORWARD-string is set up correctly. Usually, you will have an entry like this:

iptables -A FORWARD -i $EXTIF -o $INTIF -d $INTIP -m state --state ESTABLISHED,RELATED -j ACCEPT

where INTIF is your internal interface and INTIP is your IP.

This will prevent new connections. So, you should allow all forwarding for aMule-related ports:

iptables -A FORWARD -i $EXTIF -o $INTIF -p tcp --dport $EMULEPORT -d $INTIP -j ACCEPT
iptables -A FORWARD -i $EXTIF -o $INTIF -p udp --dport $EMULEUDP -d $INTIP -j ACCEPT
iptables -A FORWARD -i $EXTIF -o $INTIF -p udp --dport $EMULEUDP2 -d $INTIP -j ACCEPT