mjhjmtu

Log text from syslog(by pptpd):

Jul 18 17:25:25 user1 pppd[20577]: Using interface ppp0
Jul 18 17:25:25 user1 pppd[20577]: Connect: ppp0 <--> /dev/pts/1
Jul 18 17:25:46 user1 systemd-logind: Removed session 9232.
Jul 18 17:25:55 user1 pppd[20577]: LCP: timeout sending Config-Requests
Jul 18 17:25:55 user1 pppd[20577]: Connection terminated.
Jul 18 17:25:55 user1 pppd[20577]: Modem hangup
Jul 18 17:25:55 user1 pppd[20577]: Exit.
Jul 18 17:25:55 user1 pptpd[20575]: GRE: read(fd=6,buffer=7f9e93d50480,len=8196) from PTY failed: status = -1 error = Input/output error, usually caused by unexpected termination of pppd, check option syntax and pppd logs
Jul 18 17:25:55 user1 pptpd[20575]: CTRL: PTY read or GRE write failed (pty,gre)=(6,7)
Jul 18 17:25:55 user1 pptpd[20575]: CTRL: Client 210.109.12.126 control connection finished

Under CentOS 7.2 and PPTP package from yum, just installed and configured.
There is nothing to explain other things about errors related, even same configuration was operated well in Debian (my private laptop), but the configuration doesn't work in the server over cloud.

I can not understand why the error occurred not a routing fault and, not iptables, even not a kernel module.

[root@able-st ilovemountain]# lsmod | grep ip_gre
ip_gre 22843 0
ip_tunnel 25163 1 ip_gre
gre 12950 1 ip_gre

even the pptp daemon also not in error.

[root@able-st ilovemountain]# systemctl status pptpd
● pptpd.service - PoPToP Point to Point Tunneling Server
 Loaded: loaded (/usr/lib/systemd/system/pptpd.service; disabled; vendor preset: disabled)
 Active: active (running) since Wed 2018-07-18 17:25:18 KST; 11min ago
 Main PID: 20524 (pptpd)
 CGroup: /system.slice/pptpd.service
 └─20524 /usr/sbin/pptpd -f

Can anyone help with getting my VPN set up?