求助关于“pptpd总是掉线”的问题

[zbyzhlsp]

想学习服务器知识，于是买了个VPS，先配了个VPN。
用的pptpd

配好后可以正常验证链接，但是两三分钟后就会自动掉线。

请问各位这是什么原因？是被墙了吗？
有什么解决办法吗？

相关SYSlog如下：
Jul 26 00:22:28 www pptpd[4431]: CTRL: Client 117.79.232.158 control connection started
Jul 26 00:22:28 www pptpd[4431]: CTRL: Starting call (launching pppd, opening GRE)
Jul 26 00:22:28 www pppd[4432]: pppd 2.4.5 started by root, uid 0
Jul 26 00:22:28 www pppd[4432]: Using interface ppp0
Jul 26 00:22:28 www pppd[4432]: Connect: ppp0 <--> /dev/pts/1
Jul 26 00:22:29 www pppd[4432]: peer from calling number 117.79.232.158 authorized
Jul 26 00:22:29 www pptpd[4431]: CTRL: Ignored a SET LINK INFO packet with real ACCMs!
Jul 26 00:22:29 www pppd[4432]: local IP address 10.0.0.1
Jul 26 00:22:29 www pppd[4432]: remote IP address 10.0.0.100
Jul 26 00:23:43 www pptpd[4431]: discarding duplicate packet 3130
Jul 26 00:25:01 www CRON[4438]: (root) CMD (command -v debian-sa1 > /dev/null && debian-sa1 1 1)
Jul 26 00:27:56 www pptpd[4431]: CTRL: Session timed out, ending call
Jul 26 00:27:56 www pptpd[4431]: CTRL: Reaping child PPP[4432]
Jul 26 00:27:56 www pppd[4432]: Hangup (SIGHUP)
Jul 26 00:27:56 www pppd[4432]: Modem hangup
Jul 26 00:27:56 www pppd[4432]: Connect time 5.5 minutes.
Jul 26 00:27:56 www pppd[4432]: Sent 3757192 bytes, received 438058 bytes.
Jul 26 00:27:56 www pppd[4432]: Connection terminated.
Jul 26 00:27:56 www pppd[4432]: Exit.
Jul 26 00:27:56 www pptpd[4431]: CTRL: Client 117.79.232.158 control connection finished

[astolia]

肯定是撞墙了