例：当修改了ssh远程连接端口，如何在iptables上打开新的端口（这里将默认22端口号修改为33端口号）

#输入命令打开33端口。

[root@niaoyun ~]# iptables -I INPUT -p tcp --dport 33 -j ACCEPT

#查看防火墙规则，发现33端口号已经打开了。

[root@niaoyun ~]# iptables -nvL

Chain INPUT (policy ACCEPT 0 packets, 0 bytes)

pkts bytes target prot opt in out source destination

0 0 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp dpt:33 

295 23186 ACCEPT all -- * * 0.0.0.0/0 0.0.0.0/0 state RELATED,ESTABLISHED

34 2310 ACCEPT icmp -- * * 0.0.0.0/0 0.0.0.0/0

0 0 ACCEPT all -- lo * 0.0.0.0/0 0.0.0.0/0

2342 200K REJECT all -- * * 0.0.0.0/0 0.0.0.0/0 reject-with icmp-host-prohibited

Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)

pkts bytes target prot opt in out source destination

0 0 REJECT all -- * * 0.0.0.0/0 0.0.0.0/0 reject-with icmp-host-prohibited

Chain OUTPUT (policy ACCEPT 15 packets, 1412 bytes)

pkts bytes target prot opt in out source destination

#iptables规则已经更改，我们需要对规则进行保存。

[root@niaoyun ~]# service iptables save

iptables: Saving firewall rules to /etc/sysconfig/iptables:[ OK ]

#保存完毕，重启iptables服务。

[root@niaoyun ~]# service iptables restart

iptables: Setting chains to policy ACCEPT: filter [ OK ]

iptables: Flushing firewall rules: [ OK ]

iptables: Unloading modules: [ OK ]

iptables: Applying firewall rules: [ OK ]

#同样，用此方法也可以打开web的默认端口80

iptables -I INPUT -p tcp --dport 80 -j ACCEPT && service iptables save && service iptables restart