Iptables for Bind Squid Samba Apache Ldap Snmp Dhcp Smpt Webmin Tftp

Iptables Configuration Guide for Linux CentOS Fedora Lunux Redhat Ubuntu Debian for Bind, SSH, Squid, Samba, Apache, Ldap, Snmp, Dhcp, Smpt, SMTPS, Webmin, Tftp, HTTP HTTPS

Iptables Basic Setup:

Here I have mentioned the basic configurations for enabling iptables in fedora linux.

#iptables -L

will list your current iptables configuration.

1) To allow established sessions to receive traffic

# iptables -A INPUT -m conntrack –ctstate ESTABLISHED,RELATED -j ACCEPT

2) You could start by blocking traffic, but you might be working over SSH, where you would need to allow SSH before blocking everything else.

To allow incoming traffic on the default ssh port (22)

# iptables -A INPUT -p tcp –dport 22 -j ACCEPT

To allow incoming traffic on the default Squid port (3128)

# iptables -A INPUT -p tcp –dport 3128 -j ACCEPT

To allow incoming traffic on the default Apache port

# iptables -A INPUT -p tcp –dport 80 -j ACCEPT

To allow incoming traffic on the default samba port

# iptables -A INPUT -p udp –dport 137 -j ACCEPT
# iptables -A INPUT -p udp –dport 138 -j ACCEPT
# iptables -A INPUT -p udp –dport 139 -j ACCEPT
# iptables -A INPUT -p tcp –dport 139 -j ACCEPT
# iptables -A INPUT -p tcp –dport 445 -j ACCEPT

To allow incoming traffic on the default SNMP port (161)

# iptables -A INPUT -p tcp –dport 161 -j ACCEPT
# iptables -A INPUT -p udp –dport 161 -j ACCEPT

Now check the current configuration

# iptables -L
Chain INPUT (policy ACCEPT)
target     prot opt source               destination
ACCEPT     all — anywhere             anywhere            state RELATED,ESTABLISHED
ACCEPT     tcp — anywhere             anywhere            tcp dpt:http
ACCEPT     tcp — anywhere             anywhere            udp dpt:netbios-ns
ACCEPT     tcp — anywhere             anywhere            udp dpt:netbios-dgm
ACCEPT     tcp — anywhere             anywhere            udp dpt:netbios-ssn
ACCEPT     tcp — anywhere             anywhere            tcp dpt:netbios-ssn
ACCEPT     tcp — anywhere             anywhere            tcp dpt:snmp
ACCEPT     tcp — anywhere             anywhere            udp dpt:snmp
ACCEPT     tcp — anywhere             anywhere            tcp dpt:microsoft-ds
ACCEPT     tcp — anywhere             anywhere            tcp dpt:squid

3) Once we enabled the above port.we can drop all other incoming ports.

# iptables -A INPUT -j DROP

Now check the rule

# iptables -L

For Interface based access for eth0 specify -i eth0

4) In the final step we have to enable loopback interface. After all the traffic has been dropped. We need to insert this rule before that. Since this is a lot of traffic, we’ll insert it as the first rule so it’s processed first.

#iptables -I INPUT 1 -i lo -j ACCEPT

5) To enabling logging

# iptables -I INPUT 5 -m limit –limit 5/min -j LOG –log-prefix “iptables denied: ” –log-level 7

6) To save this configuration

# iptables-save > /etc/sysconfig/iptables
or
#service iptables save

#service iptables start

This configuration will enable ssh port and disable all other incoming ports.

To manually edit iptables config

Also you can manual edit /etc/sysconfig/iptables

IP Tables configuration for other Services

1) Iptables for LDAP / LDAPS / OPENLDAP

# iptables -A INPUT -p tcp –dport 389 -j ACCEPT
# iptables -A INPUT -p tcp –dport 636 -j ACCEPT