Iptables is one of the simple firewall that we can use as a server administrator. Especially in Linux server computer.
In this example I want to redirect port 8080 or 80 to 3128 which is port for proxy squid that I have.
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iptables -t nat -A PREROUTING -i eth0 -p tcp -m tcp –dport 80 -j REDIRECT –to-ports 3128
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iptables -t nat -A PREROUTING -i eth0 -p tcp -m tcp –dport 8080 -j REDIRECT –to-ports 3128
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iptables-save
Just remember to do it in root access (administrator).