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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.
Enter the secondary DNS server address here: 202.96.209.133 第二个 DNS 建议手动设置，不然可能连不上
PASSWORD
Please enter your Password: 输入 ADSL 的连接密码
Please re-enter your Password: ← 再次确认输入 ADSL 的连接密码
USERCTRL
Please enter 'yes' (three letters, lower-case.) if you want to allow
normal user to start or stop DSL connection (default yes): yes← 填入 no，不允许一般用户控制 PPPoE 的连接
FIREWALLING
Please choose the firewall rules to use. Note that these rules are
very basic. You are strongly encouraged to use a more sophisticated
firewall setup; however, these will provide basic security. If you
are running any servers on your machine, you must choose 'NONE' and
set up firewalling yourself. Otherwise, the firewall rules will deny
access to all standard servers like Web, e-mail, ftp, etc. If you
are using SSH, the rules will block outgoing SSH connections which
allocate a privileged source port.
The firewall choices are:
0 - NONE: This script will not set any firewall rules. You are responsible
for ensuring the security of your machine. You are STRONGLY
recommended to use some kind of firewall rules.
1 - STANDALONE: Appropriate for a basic stand-alone web-surfing workstation
2 - MASQUERADE: Appropriate for a machine acting as an Internet gateway
for a LAN
Choose a type of firewall (0-2): 0← 输入 0，不在这里使用防火墙
Start this connection at boot time
Do you want to start this connection at boot time?
Please enter no or yes (default no):yes← 填入 yes，在系统启动时自动连接 ADSL
Accept these settings and adjust configuration files (y/n)? y← 配置信息确认无误后，键入 y 同意设置
** Summary of what you entered **
Ethernet Interface:eth0
User name:
[root@localhost ~]# pppoe-start← 启动 ADSL pppoe 连接（或# ifup ppp0 // 启动 ppp0 接口）
[root@localhost ~]# pppoe-status 设置完成后我们看看 adsl 状态
