安装相关软件
apt install network-manager-pptp-gnome
#sudo apt-get install network-manager-pptp
sudo apt-get install pptp-linux
编辑VPN，Gateway填VPN服务器IP或域名，username password 是VPN用户名和密码。
如果VPN服务器是windows，还要单击“高级”按钮，验证方式只钩MSCHAP和MSCHAPv2
不能禁用EAP认证方式,所以还要按照下面的方法更改：
连接到windows server 2003 vpn
新立得里搜索pptp，安装
创建pptp连接
高级设置：认证方式只钩MSCHAPv2，钩上“使用MPPE”，选择128位
这三个要同时存在才行！如果连接失败，再看看是否配置正确。
或：用终端进gconf-editor ，system-networking-connections，展开那些123.看到有VPN的，
有如下require-mppe-128 yes,refuse-pap yes,refuse-eap yes,refuse-chap yes即可
#一开始这样
Using interface ppp0
Connect: ppp0 <--> /dev/pts/5
CHAP authentication succeeded
LCP terminated by peer (MPPE required but peer refused)
Script pptp bestfreevpn.com –nolaunchpppd finished (pid 18395), status = 0x0
Modem hangup
Connection terminated.
http://wiki.ubuntu.org.cn/VPN
http://forum.ubuntu.org.cn/viewtopic.php?t=280231
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Now add a VPN user in /etc/ppp/chap-secrets file.
# sudo nano /etc/ppp/chap-secrets
The column is username. Second column is server name, you can put “pptpd” in there. Third column is password. The last column is the IP addresses, you can put * to allow all IP.
# client server secret IP addresses
username * myPassword *
vim /etc/ppp/chap-secrets
“evan” pptpd “1234” *
pptp 11.12.33.44
sudo pptpsetup –create myvpn –server xxx.xxx.xxx.xxx –username xx1 –password xx2–encrypt –start
sudo pptpsetup –create myvpn –server “” –username –password “” –encrypt –start
pptp ip noauth require-mppe-128 name uname nodetach mtu 1416
