CentOS上网真是个麻烦的事情，它不像Ubuntu一样在安装时就能配置好网络，它会出现各种问题。
首先我的电脑直接插网线后，ifconfig显示找不到eth0。后来仔细一看网线接口根本不亮！后来找了半天终于把驱动找到了，装完驱动插入内核模块后，网线接口亮了，ifconfig也能显示eth0了，说明硬件搞定。【该步骤详情参考这里】
下面是重点，我折腾了半天还是上不去网，后来发现了一些教程说安装一个叫rp-pppoe的拨号软件，于是我安装了，结果还是不行，NetworkManager和network服务重启了无数次还是不行，setup里面改了又改还是不行，我以为要用DHCP服务，还特地安装了DHCP，结果配置不了，比较复杂，毕竟我课程还没到网络原理～于是在拨号失败，DHCP又不会配置时我崩溃了，放弃了一段时间。今晚再次想起来了，心想一定要搞定它!参考这篇文章（），里面说rp-pppoe不需要NetworkManager，可以卸载NetworkManager，我心想，我读书少你可别骗我，NetworkManager卸载后连个网络图标都没了，还连个毛毛网。
看完后不敢轻信，但又想试试，于是结合另一篇教程（），开始了终极实验。我特地准备了四个DNS地址，我下决心不用DHCP了，因为从百度百科上看DHCP用于配置局域网，我反正又不用路由器。
四个DNS分别为：
百度公共DNS：180.76.76.76
阿里云公共DNS：223.5.5.5、223.6.6.6
四川省成都市教育网DNS（博主在成都上学）：202.115.64.34
然后开终端，配置rp-pppoe，运行命令
pppoe-setup
以下为具体过程（#后面的中文是我写的注释）：
[root@KD src]# pppoe-setup
Welcome to the Roaring Penguin PPPoE client setup. First, I will run
some checks on your system to make sure the PPPoE client is installed
properly...
Looks good! Now, please enter some information:
USER NAME
>>> Enter your PPPoE user name (default bp20122999@cer): #帐号填你的帐号（教育网、网通、电信均可）
INTERFACE
>>> Enter the Ethernet interface connected to the DSL modem
For Solaris, this is likely to be something like /dev/hme0.
For Linux, it will be ethn, where 'n' is a number.
(default eth0): #默认为eth0，可以直接回车默认，或者多此一举手写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): #不管这步，直接回车
DNS
Please enter the IP address of your ISP's primary DNS server.
If your ISP claims that 'the server will provide 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: 223.5.5.5 #主DNS（上面四个DNS选一个，自己搞其他的也行）
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: 223.6.6.6 #备用DNS
PASSWORD
>>> Please enter your PPPoE password: #你滴密码
>>> Please re-enter your PPPoE password: #再输一次
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.