Port Forwarding in CentOS Using Iptables

check if IP forwarding is enabled:

/sbin/sysctl net.ipv4.ip_forward

if return
net.ipv4.ip_forward = 1
then it is enabled. if not edit /etc/sysctl.conf and set net.ipv4.ip_forward = 1
rerun

/sbin/sysctl -p /etc/sysctl.conf

/sbin/service iptables restart

Adding IP forwarding rules to IpTables

/sbin/iptables -I FORWARD 1 -m state --state ESTABLISHED,RELATED -j ACCEPT

/sbin/iptables -I FORWARD 1 -p tcp --dport 80 -j ACCEPT

/sbin/iptables -t nat -A PREROUTING -p tcp --dport 80 -j DNAT --to-destination 10.0.1.1:8080

/sbin/iptables -t nat -A POSTROUTING -j MASQUERADE

/sbin/service iptables save

/sbin/service iptables restart

 

The content of /etc/sysconfig/iptables files looks like:




# Generated by iptables-save v1.3.5 on Fri Mar  8 10:27:21 2013

*nat

:PREROUTING ACCEPT [0:0]

:POSTROUTING ACCEPT [0:0]

:OUTPUT ACCEPT [0:0]

-A PREROUTING -p tcp -m tcp --dport 80 -j DNAT --to-destination 10.0.1.1:8080

-A POSTROUTING -j MASQUERADE

COMMIT

# Completed on Fri Mar  8 10:27:21 2013

# Generated by iptables-save v1.3.5 on Fri Mar  8 10:27:21 2013

*filter

:INPUT ACCEPT [0:0]

:FORWARD ACCEPT [0:0]

:OUTPUT ACCEPT [234:26336]

:RH-Firewall-1-INPUT - [0:0]

-A INPUT -j RH-Firewall-1-INPUT

-A FORWARD -p tcp -m tcp --dport 80 -j ACCEPT

-A FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT

-A FORWARD -j RH-Firewall-1-INPUT

-A RH-Firewall-1-INPUT -i lo -j ACCEPT

-A RH-Firewall-1-INPUT -p icmp -m icmp --icmp-type any -j ACCEPT

-A RH-Firewall-1-INPUT -p esp -j ACCEPT

-A RH-Firewall-1-INPUT -p ah -j ACCEPT

-A RH-Firewall-1-INPUT -p udp -m udp --dport 631 -j ACCEPT

-A RH-Firewall-1-INPUT -p tcp -m tcp --dport 631 -j ACCEPT

-A RH-Firewall-1-INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT

-A RH-Firewall-1-INPUT -p tcp -m state --state NEW -m tcp --dport 22 -j ACCEPT

-A RH-Firewall-1-INPUT -p tcp -m state --state NEW -m tcp --dport 137 -j ACCEPT

-A RH-Firewall-1-INPUT -p tcp -m state --state NEW -m tcp --dport 138 -j ACCEPT

-A RH-Firewall-1-INPUT -p tcp -m state --state NEW -m tcp --dport 139 -j ACCEPT

-A RH-Firewall-1-INPUT -p tcp -m state --state NEW -m tcp --dport 443 -j ACCEPT

-A RH-Firewall-1-INPUT -p tcp -m state --state NEW -m tcp --dport 445 -j ACCEPT

-A RH-Firewall-1-INPUT -p tcp -m state --state NEW -m tcp --dport 80 -j ACCEPT

-A RH-Firewall-1-INPUT -p tcp -m state --state NEW -m tcp --dport 8080 -j ACCEPT

-A RH-Firewall-1-INPUT -p tcp -m state --state NEW -m tcp --dport 8082 -j ACCEPT

-A RH-Firewall-1-INPUT -p tcp -m state --state NEW -m tcp --dport 5432 -j ACCEPT

-A RH-Firewall-1-INPUT -p tcp -m state --state NEW -m tcp --dport 50010 -j ACCEPT

-A RH-Firewall-1-INPUT -p tcp -m state --state NEW -m tcp --dport 50030 -j ACCEPT

-A RH-Firewall-1-INPUT -p tcp -m state --state NEW -m tcp --dport 50060 -j ACCEPT

-A RH-Firewall-1-INPUT -p tcp -m state --state NEW -m tcp --dport 50070 -j ACCEPT

-A RH-Firewall-1-INPUT -p tcp -m state --state NEW -m tcp --dport 54310 -j ACCEPT

-A RH-Firewall-1-INPUT -p tcp -m state --state NEW -m tcp --dport 50075 -j ACCEPT

-A RH-Firewall-1-INPUT -j REJECT --reject-with icmp-host-prohibited

 

 

 

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