Linux 系统怎么用电信宽带拨号上网

（1）安装的前提条件

<1>确保安装了网卡并工作正常

使用命令
#ifconfig eth0
查看网卡状态

<2>在系统中不要设置默认路由(网关),让ADSL拨号后自动获得

如果已经设置了默认路由,使用以下方法删除:
在文件 /etc/sysconfig/network/ifconfig-eth0 中删除 GATEWAY= 这一行,然后以root执行:

# service network restart

<3>已经安装了pppd软件包

如果存在文件 /usr/sbin/pppd,则说明已经安装了pppd; 如果未安装,下载安装这个软件包。

（2）安装PPPOE客户端软件

Linux下的PPPOE客户端软件比较多,而且大多使用GNU License,我们推荐使用rp-pppoe
这个软件包。从http://www.roaringpenguin.com/products/pppoe这个网站上，不仅可以下载
各发布包下的rp-pppoe的二进制软件包，而且可以下载源代码软件包。

我们使用centos下的yum安装方法,来安装rp-pppoe软件包
#yum install rp-pppoe

（3）配置PPPOE客户端软件

<1>配置文件

安装完软件包后，必须配置PPPOE的配置文件/etc/ppp/pppoe.conf，从而让ADSL拨号时使用配置文件中的用户名、密码等参数。

<2>命令配置
# adsl-setup ← 建立ADSL连接

Welcome to the ADSL client setup. First, I will run some checks on
your system to make sure the PPPoE client is installed properly...

LOGIN NAME

Enter your Login Name (default root): ← 填入ADSL连接的用户名

INTERFACE

Enter the Ethernet interface connected to the ADSL 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): ← 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

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: ← 如果知道DNS服务器的信息在此填入。不知道的情况按回车跳过

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' (two letters, lower-case.) if you want to allow
normal user to start or stop DSL connection (default yes): no ← 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

** Summary of what you entered **

Ethernet Interface: eth0
User name: caun870293@ca.dti.ne.jp
Activate-on-demand: No
DNS: Do not adjust
Firewalling: NONE
User Control: no
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
Adjusting /etc/sysconfig/network-scripts/ifcfg-ppp0
Adjusting /etc/ppp/chap-secrets and /etc/ppp/pap-secrets
(But first backing it up to /etc/ppp/chap-secrets.bak)
(But first backing it up to /etc/ppp/pap-secrets.bak)

?

Congratulations, it should be all set up!

Type '/sbin/ifup ppp0' to bring up your xDSL link and '/sbin/ifdown ppp0'
to bring it down.
Type '/sbin/adsl-status /etc/sysconfig/network-scripts/ifcfg-ppp0'
to see the link status.

（4）启动PPPOE客户端软件
# adsl-start ← 启动ADSL连接
# ← 稍等片刻后若启动成功后出现提示符（无任何提示或Connected意味着连接成功）

如果不成功，请检查网线、ADSL MODEM等物理设备，并查看 /var/log/messages中的信息
/usr/sbin/adsl-stop 关闭和ISP的连接
/usr/sbin/adsl-status 查看当前连接的状态

如果想在Linux系统启动时自动启动ADSL连接，输入以下命令
#chkconfig --add adsl
将在当前的运行级下加入ADSL的自启动脚本

（5）测试
当连接成功后，使用命令 #ifconfig -a 在输出中应该含有关于 ppp0 的一堆信息，其中还绑定了 IP 地址,说明已经从拨号中获 得了IP地址。使用命令 #netstat -nr 查看路由表信息，这时的默认路由应该是上面获得的IP地址。 如果没有默认路由，我们可以手动增加： #route add default gw 上面获得的IP地址使用命令#nslookup www.sina.com.cn 如果解析出新浪的IP，说明已经从拨号中正确获得了DNS服务器最后，使用命令ping某个域名或IP，如果有响应，表示你已经大功告成了。

参考http://z.baidu.com/question/117454426.html?fr=qrl&cid=89&index=2