CentOS6以后要安装rp-pppoe这个软件，centos之前的版本是adsl-setup命令安装。
（1）查看是否安装
#rpm -qa|grep rp-pppoe
没有内容输出则没安装，若可以联网使用# yum install rp-pppoe
无法联网则：CentOS安装盘放入光驱
挂载光盘
#mount /dev/cdrom /media
找出文件路径
# find /media -name 'rp-pppoe*'
这个文件没有依赖项，可以直接安装
#rpm -ivh /media/CentOS_6.5_Final/Packages/rp-pppoe-3.10-8.el6.i686.rpm
（2）设置拨号
#whereis pppoe-setup
#/sbin/pppoe-setup
或#pppoe-setup
开始设置ADSL和DNS信息：
Welcome to the PPPoE client setup. First, I will run some checks on
your system to make sure the PPPoE client is installed properly...
The following DSL config was found on your system:
Device: Name:
ppp0 DSLppp0
Please enter the device if you want to configure the present DSL config
(default ppp0) or enter 'n' if you want to create a new one: ppp0
LOGIN NAME
Enter your Login Name (default root): 中国电信或者网通给你的ADSL用户名，注意电信给的有ad打头
INTERFACE
Enter the Ethernet interface connected to the PPPoE modem
For Solaris, this is likely to be something like /dev/hme0.
For Linux, it will be ethX, where 'X' is a number.
(default eth0): eth0← 指定网络接入设备，一块网卡的情况下，一般为默认eth0
Do you want the link to come up on demand, or stay up continuously?
If you want it to come up on demand, enter the idle time in seconds
after which the link should be dropped. If you want the link to
stay up permanently, enter 'no' (two letters, lower-case.)
NOTE: Demand-activated links do not interact well with dynamic IP
addresses. You may have some problems with demand-activated links.
Enter the demand value (default no): ← 直接按回车，接受默认设置，询问的是，adsl连接以后，是否持续保持连接。或者是自动的断开，在指定的时间（以秒数计算）内。多数情况下，我们希望手动的打开关闭连接。所以这里选择默认的no。
DNS
Please enter the IP address of your ISP's primary DNS server.
If your ISP claims that 'the server will provide dynamic DNS addresses',
enter 'server' (all lower-case) here.
If you just press enter, I will assume you know what you are
doing and not modify your DNS setup.
Enter the DNS information here: 202.96.209.5 第一个DNS建议手动设置，不然可能连不上（或Enter the DNS information here: server //PPPOE拨号的输入server即可，即动态获得DNS）
Please enter the IP address of your ISP's secondary DNS server.
If you just press enter, I will assume there is only one DNS server.
