iptables common configuration finishing

Sort out the common configuration of iptables under centos

1. View all iptables configurations

 

iptables -L -n

 

2. Add a rule to allow INPUT access. The following are the port settings for common services. If you need to deny access, change ACCEPT to DROP.

wrote

#SSH
iptables -A INPUT -p tcp --dport 22 -j ACCEPT
#HTTP
iptables -A INPUT -p tcp --dport 80 -j ACCEPT
iptables -A INPUT -p tcp --dport 8080 -j ACCEPT
#HTTPS
iptables -A INPUT -p tcp --dport 443 -j ACCEPT
#POP3
iptables -A INPUT -p tcp --dport 110 -j ACCEPT
#SMTP
iptables -A INPUT -p tcp --dport 25 -j ACCEPT
#FTP
iptables -A INPUT -p tcp --dport 21 -j ACCEPT
iptables -A INPUT -p tcp --dport 20 -j ACCEPT
#DNS
iptables -A INPUT -p tcp --dport 53 -j ACCEPT

 

3. Add a rule to restrict INPUT access using IP, here take SSH as an example, 192.168.0.100 is the allowed IP

 

wrote

#DELETE
iptables -D INPUT -p tcp --dport 22 -j ACCEPT
#ADD
iptables -A INPUT -s 192.168.0.100 -p tcp --dport 22 -j ACCEPT

 

4. Save the iptables settings, remember to save after modifying the rules

 

 /etc/rc.d/init.d/iptables save

5. Restart iptables

 

 service iptables restart

6. Turn on/off boot up

 

chkconfig iptables on

chkconfig iptables off

7. Open the iptables configuration file:

 

 

vi /etc/sysconfig/iptables 

Use the /etc/init.d/iptables status command to check whether port 80 is opened. If not, there are two ways to deal with it:

8. Modify the vi /etc/sysconfig/iptables command to add the firewall to open port 80

 

 

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

 

9. Turn off/on/restart the firewall

 

/etc/init.d/iptables stop 

#start start

#restart restart

10. Permanently turn off the firewall

 

 

 chkconfig --level 35 iptables off 

 /etc/init.d/iptables stop  

    

iptables -P INPUT DROP

11. Open port 21 in active mode

 

 

iptables -A INPUT -p tcp --dport 21 -j ACCEPT

12. Open ports between 49152 and 65534 in passive mode

 

 

wrote

iptables -A INPUT -p tcp --dport 49152:65534 -j ACCEPT

iptables -A INPUT -i lo -j ACCEPT

iptables -A INPUT -m state --state ESTABLISHED -j ACCEPT

 

 

Restart iptables after all modifications are made:

 

 

service iptables restart 

You can verify that the rules are in effect:

 

How to manually change the config file:

wrote

[root@CentOS ~]# vi /etc/sysconfig/iptables
# Firewall configuration written by system-config-firewall
# Manual customization of this file is not recommended.
*filter
:INPUT ACCEPT [0:0]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [0:0]
-A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
-A INPUT -p icmp -j ACCEPT
-A INPUT -i lo -j ACCEPT
-A INPUT -m state --state NEW -m tcp -p tcp --dport 22 -j ACCEPT
-A INPUT -m state --state NEW -m tcp -p tcp --dport 80 -j ACCEPT
-A INPUT -j REJECT --reject-with icmp-host-prohibited
-A FORWARD -j REJECT --reject-with icmp-host-prohibited
COMMIT

 

 

[root@CentOS ~]# /etc/init.d/iptables restart