IPTables/NFTables
NFTables
Resources
IPTables
Port Forwarding
Something like:
iptables -t nat -A PREROUTING -i eth0 -p tcp --dport 4040:4049 -j DNAT --to-destination 10.13.37.4
Forwards ports 4040-4049 to 10.13.37.44
IPTables Connection Forwarding
This is basically an in-kernel connection proxy.
echo 1 > /proc/sys/net/ipv4/ip_forward
iptables -P FORWARD DROP
PROXY_IP=10.1.1.1
PROXY_PORT=4444
TARGET_IP=10.2.2.2
TARGET_PORT=6666
iptables -A FORWARD -p tcp -d ${TARGET_IP} --dport ${TARGET_PORT} -j ACCEPT
iptables -A FORWARD -m state --state ESTABLISHED,RELATED -j ACCEPT
iptables -t nat -A PREROUTING --dst ${PROXY_IP} -p tcp --dport ${PROXY_PORT} \
-j DNAT --to-destination ${TARGET_IP}:${TARGET_PORT}
iptables -t nat -A POSTROUTING -p tcp --dst ${TARGET_IP} \
--dport ${TARGET_PORT} -j SNAT --to-source ${PROXY_IP}
iptables -t nat -A OUTPUT --dst ${PROXY_IP} -p tcp --dport ${PROXY_PORT} \
-j DNAT --to-destination ${TARGET_IP}:${TARGET_PORT}
IPTables Flow
