1.服务器
查看系统版本
cat /etc/redhat-release操作系统：CentOS Linux release 7.7.1908 (Core)
IP地址：122.51.8.56
2、客户端
windows10操作系统，手机端
1、确定内核是否支持mppe
modprobe ppp-compress-18 && echo good!如果输出good！，那么支持mppe，否则需要升级内核支持mppe，自行百度。
2、检查ppp是否开启
cat /dev/ppp3、安装ppp和pptpd
yum install ppp && yum install pptpd4、编写配置文件
客户端分配的内网ip段
vi /etc/pptpd.conf将#号去掉，或自行配置
配置dns
vi /etc/ppp/options.pptpd这里我用的是谷歌的dns，可以有两个，第二个是备用的，自行选择。
修改日志记录 ，方便查找错误（在文件最后）
5、添加用户登录的用户名及密码
vi /etc/ppp/chap-secrets格式为
用户名 pptpd 密码 * 中间用tab键隔开
6、修改内核参数，使服务器可以转发
vi /etc/sysctl.conf将net.ipv4.ip_forward=0修改为1，保存退出
sysctl -p#使内核参数生效7.添加iptables转发规则
iptables -t nat -A POSTROUTING -s 192.168.0.0/24 -o eth0 -j MASQUERADE重启后会失效，修改/etc/rc.d/rc.local保存上面的命令，这样开机会自动执行上面的命令。
8.开机自启
chkconfig pptpd on#开机自启 systemctl restart pptpd#重启三、使用
使用win10自带的vpn，或者手机自带的vpn尝试连接，但是一直没有成功。
并且日志一直报这个错误。
Plugin /usr/lib64/pptpd/pptpd-logwtmp.so loaded. pptpd-logwtmp: $Version$ pppd options in effect: debug # (from /etc/ppp/options.pptpd) logfile /var/log/pptpd.log # (from /etc/ppp/options.pptpd) dump # (from /etc/ppp/options.pptpd) plugin /usr/lib64/pptpd/pptpd-logwtmp.so # (from command line) require-mschap-v2 # (from /etc/ppp/options.pptpd) refuse-pap # (from /etc/ppp/options.pptpd) refuse-chap # (from /etc/ppp/options.pptpd) refuse-mschap # (from /etc/ppp/options.pptpd) name pptpd # (from /etc/ppp/options.pptpd) remotenumber 117.136.92.127 # (from command line) pptpd-original-ip 117.136.92.127 # (from command line) 115200 # (from command line) lock # (from /etc/ppp/options.pptpd) local # (from command line) novj # (from /etc/ppp/options.pptpd) novjccomp # (from /etc/ppp/options.pptpd) ipparam 117.136.92.127 # (from command line) ms-dns xxx # [don't know how to print value] # (from /etc/ppp/options.pptpd) proxyarp # (from /etc/ppp/options.pptpd) 192.168.0.1:192.168.0.234 # (from command line) nobsdcomp # (from /etc/ppp/options.pptpd) require-mppe-128 # (from /etc/ppp/options.pptpd) using channel 22 Using interface ppp0 Connect: ppp0 <--> /dev/pts/4 sent [LCP ConfReq id=0x1 <asyncmap 0x0> <auth chap MS-v2> <magic 0x273a897f> <pcomp> <accomp>] sent [LCP ConfReq id=0x1 <asyncmap 0x0> <auth chap MS-v2> <magic 0x273a897f> <pcomp> <accomp>] sent [LCP ConfReq id=0x1 <asyncmap 0x0> <auth chap MS-v2> <magic 0x273a897f> <pcomp> <accomp>] sent [LCP ConfReq id=0x1 <asyncmap 0x0> <auth chap MS-v2> <magic 0x273a897f> <pcomp> <accomp>] sent [LCP ConfReq id=0x1 <asyncmap 0x0> <auth chap MS-v2> <magic 0x273a897f> <pcomp> <accomp>] sent [LCP ConfReq id=0x1 <asyncmap 0x0> <auth chap MS-v2> <magic 0x273a897f> <pcomp> <accomp>] sent [LCP ConfReq id=0x1 <asyncmap 0x0> <auth chap MS-v2> <magic 0x273a897f> <pcomp> <accomp>] sent [LCP ConfReq id=0x1 <asyncmap 0x0> <auth chap MS-v2> <magic 0x273a897f> <pcomp> <accomp>] sent [LCP ConfReq id=0x1 <asyncmap 0x0> <auth chap MS-v2> <magic 0x273a897f> <pcomp> <accomp>] sent [LCP ConfReq id=0x1 <asyncmap 0x0> <auth chap MS-v2> <magic 0x273a897f> <pcomp> <accomp>] LCP: timeout sending Config-Requests Connection terminated. Modem hangup