编辑iptables配置文件，将文件内容更改为如下，则具备了ip地址白名单功能
#vim /etc/sysconfig/iptables
*filter
:INPUT ACCEPT [0:0]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [0:0]
-N whitelist
-A whitelist -s 1.2.3.0/24 -j ACCEPT
-A whitelist -s 4.5.6.7 -j ACCEPT
-A INPUT -m state --state RELATED,ESTABLISHED -j whitelist
-A INPUT -m
