Port Redirection through the iptables

Article by Aashish

How do I redirect 80 port to 8123 using iptables?

You can easily redirect incoming traffic by inserting rules into PREROUTING chain of the nat table. You can set destination port using the REDIRECT target.

Syntax

The syntax is as follows to redirect tcp $srcPortNumber port to $dstPortNumber:

iptables -t nat -A PREROUTING -i eth0 -p tcp –dport $srcPortNumber -j REDIRECT –to-port $dstPortNumbe

The syntax is as follows to redirect udp $srcPortNumber port to $dstPortNumber:

iptables -t nat -A PREROUTING -i eth0 -p udp –dport $srcPortNumber -j REDIRECT –to-port $dstPortNumber

Replace eth0 with your actual interface name. The following syntax match for source and destination ips:

iptables -t nat -I PREROUTING –src $SRC_IP_MASK –dst $DST_IP -p tcp –dport $portNumber -j REDIRECT –to-ports $rediectPort

Examples:

In The following example redirects TCP port 25 to port 2525:

# iptables -t nat -A PREROUTING -i eth0 -p tcp –dport 25 -j REDIRECT –to-port 2525

this example all incoming traffic on port 80 redirect to port 8123

# iptables -t nat -I PREROUTING –src 0/0 –dst 192.168.1.5 -p tcp –dport 80 -j REDIRECT –to-ports 8123

How Do I View NAT Rules?

Type the following command:

# iptables -t nat -L -n -v

How Do I Save NAT Redirect Rules?

Type the following command:

# iptables-save

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