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@humengyun ~]# 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@humengyun ~]# 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@humengyun ~]# service iptables save
iptables: Saving firewall rules to /etc/sysconfig/iptables:[ OK ]
#保存完毕，重启iptables服务。
[root@humengyun ~]# 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