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5.8

Using IPTABLE and NAT to send mail through Specific Mail Server

Asked by tapesh_kumar in Linux Network Security

Tags: iptable

Hi!

I am using Red Hat Linux 4 as my Linux Gateway for my client machines.

I have configured SQUID for monitoring HTTP traffic and using these three commands to use NAT:

iptables --table nat --append POSTROUTING --out-interface eth0 -j MASQUERADE
iptables --append FORWARD --in-interface eth1 -j ACCEPT
echo 1 > /proc/sys/net/ipv4/ip_forward
iptables -t nat -A PREROUTING -p tcp --dport 80 -j REDIRECT --to-port 3128

Now my question is that my cleint will be able to send mails onl;y when they use my Mail SERVER ADDRESS i.e., 203.101.80.6.

Mine iptable file is given below:

But its not working

# Firewall configuration written by system-config-securitylevel
# Manual customization of this file is not recommended.
*filter
:INPUT ACCEPT [0:0]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [0:0]
:RH-Firewall-1-INPUT - [0:0]
:RH-Firewall-1-OUTPUT - [0:0]
-A OUTPUT -j RH-Firewall-1-OUTPUT
-A INPUT -j RH-Firewall-1-INPUT
-A FORWARD -j RH-Firewall-1-INPUT
#-A RH-Firewall-1-OUTUT -i eth0 -j ACCEPT
-A RH-Firewall-1-INPUT -i lo -j ACCEPT
-A RH-Firewall-1-INPUT -i eth1 -j ACCEPT
#-A RH-Firewall-1-INPUT -p icmp --icmp-type any -j ACCEPT
-A RH-Firewall-1-INPUT -p 50 -j ACCEPT
-A RH-Firewall-1-INPUT -p 51 -j ACCEPT
-A RH-Firewall-1-INPUT -p udp --dport 5353 -d 224.0.0.251 -j ACCEPT
-A RH-Firewall-1-INPUT -p udp -m udp --dport 631 -j ACCEPT
-A RH-Firewall-1-INPUT -p tcp -m tcp --syn -s 195.22.3.46 --dport 22 -j ACCEPT
-A RH-Firewall-1-INPUT -p tcp -m tcp --syn -s 195.22.3.138 --dport 22 -j ACCEPT
-A RH-Firewall-1-INPUT -i eth0 -p tcp -m state --state ESTABLISHED -d ! 203.101.80.6 --sport 25 -j DROP
-A RH-Firewall-1-OUTPUT -o eth0 -p tcp -m state --state NEW,ESTABLISHED -d ! 203.101.80.6 --dport 25 -j DROP
-A RH-Firewall-1-INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
-A RH-Firewall-1-INPUT -j REJECT --reject-with icmp-host-prohibited
COMMIT

Kindly help me out..

Early reply will be appreciated.

Thanks & Regards

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Using IPTABLE and NAT to send mail through Specific Mail Server

Asked by tapesh_kumar in Linux Network Security

Tags: iptable

About this solution