CentOS 6
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iptables - Setting Example #1
2013/07/28
 
This is an Example of setting iptables on the Server below. 
                      Internet
                          |
                    +----------+
--------------------|  Router  |----------------------
                    +----------+
                          |
                  LAN(10.0.0.0/24)
+----------+              |               +----------+
|          |              |     10.0.0.100|          |
|    PC    |------------------------------|  Server  |
|          |                          eth0|          |
+----------+                              +----------+
 
* DROP INPUT by Default
* ACCEPT OUTPUT by Default
* ACCEPT Established Connection
* ACCEPT the Connection from loopback
* ACCEPT Ping Connection for 5 times per a minites from internal network(10.0.0.0/24)
* ACCEPT SSH Connection from internal network(10.0.0.0/24)
[1] Configure iptables
[root@dlp ~]#
vi iptables.sh 
#!/bin/bash

trust_host='10.0.0.0/24'
my_host='10.0.0.100'

/sbin/iptables -F
/sbin/iptables -X

/sbin/iptables -P INPUT DROP
/sbin/iptables -P OUTPUT ACCEPT
/sbin/iptables -P FORWARD DROP

/sbin/iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT

/sbin/iptables -A INPUT -s 127.0.0.1 -d 127.0.0.1 -j ACCEPT

/sbin/iptables -A INPUT -p icmp --icmp-type echo-request -s $trust_host \
-d $my_host -m limit --limit 1/m --limit-burst 5 -j ACCEPT

/sbin/iptables -A INPUT -p tcp -m state --state NEW -m tcp -s $trust_host \
-d $my_host --dport 22 -j ACCEPT

/etc/rc.d/init.d/iptables save
/etc/rc.d/init.d/iptables restart
[root@dlp ~]#
sh iptables.sh 

iptables: Saving firewall rules to /etc/sysconfig/iptables: [  OK  ]
iptables: Flushing firewall rules: [  OK  ]
iptables: Setting chains to policy ACCEPT: filter [  OK  ]
iptables: Unloading modules: [  OK  ]
iptables: Applying firewall rules: ip_tables: (C) 2000-2006 Netfilter Core Team
nf_conntrack version 0.5.0 (16384 buckets, 65536 max)
[  OK  ]
 
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