Pptpd vpn Problems

Pptpd vpn problems-Linux Enterprise Application-Linux server application information, the following is a detailed description. Who can help me?
Dec 14 12:26:05 chen pppd [6782]: Plugin/usr/lib/pptpd/pptpd-logwtmp.so loaded.

Dec 14 12:26:05 chen pppd [6782]: The remote system is required to authenticate itself
Dec 14 12:26:05 chen pppd [6782]: but I couldn't find any suitable secret (password) for it to use to do so
Dec 14 12:26:05 chen pptpd [6781]: GRE: read (fd = 6, buffer = 8059680, len = 8196) from PTY failed: status =-1 error = Input/output error, usually caused by unexpected termination of pppd, check option syntax and pppd logs

Dec 14 12:26:05 chen pptpd [6781]: CTRL: PTY read or GRE write failed (pty, gre) = (6, 7)
Dec 14 12:26:05 chen pptpd [6781]: CTRL: Client 192.168.102.108 control connection finished

Dec 14 12:28:20 chen pptpd [6848]: MGR: Maximum of 100 connections reduced to 5, not enough IP addresses given

Dec 14 12:28:20 chen pptpd [6849]: MGR: Manager process started

Dec 14 12:28:20 chen pptpd [6849]: MGR: Maximum of 5 connections available
Dec 14 12:28:21 chen pptpd [6877]: MGR: Maximum of 100 connections reduced to 5, not enough IP addresses given

Dec 14 12:28:21 chen pptpd [6878]: MGR: Manager process started

Dec 14 12:28:21 chen pptpd [6878]: MGR: Maximum of 5 connections available

Dec 14 12:28:28 chen pptpd [6880]: CTRL: Client 192.168.102.108 control connection started

Dec 14 12:28:28 chen pptpd [6880]: CTRL: Starting call (launching pppd, opening GRE)

Dec 14 12:28:28 chen pppd [6881]: In file/etc/ppp/options.ppt pd: unrecognized option 'require'

Dec 14 12:28:28 chen pptpd [6880]: GRE: read (fd = 6, buffer = 8059680, len = 8196) from PTY failed: status =-1 error = Input/output error, usually caused by unexpected termination of pppd, check option syntax and pppd logs

Dec 14 12:28:28 chen pptpd [6880]: CTRL: PTY read or GRE write failed (pty, gre) = (6, 7)

Dec 14 12:28:28 chen pptpd [6880]: CTRL: Client 192.168.102.108 control connection finished

Dec 14 12:28:29 chen pptpd [6882]: CTRL: Client 192.168.102.108 control connection started

Dec 14 12:28:29 chen pptpd [6882]: CTRL: Starting call (launching pppd, opening GRE)

Dec 14 12:28:29 chen pppd [6883]: In file/etc/ppp/options.ppt pd: unrecognized option 'require'

Dec 14 12:28:29 chen pptpd [6882]: GRE: read (fd = 6, buffer = 8059680, len = 8196) from PTY failed: status =-1 error = Input/output error, usually caused by unexpected termination of pppd, check option syntax and pppd logs

Dec 14 12:28:29 chen pptpd [6882]: CTRL: PTY read or GRE write failed (pty, gre) = (6, 7)

Dec 14 12:28:29 chen pptpd [6882]: CTRL: Client 192.168.102.108 control connection finished

Dec 14 12:28:42 chen pptpd [6884]: CTRL: Client 192.168.102.108 control connection started

Dec 14 12:28:42 chen pptpd [6884]: CTRL: Starting call (launching pppd, opening GRE)

Dec 14 12:28:42 chen pppd [6885]: In file/etc/ppp/options.ppt pd: unrecognized option 'require'

Dec 14 12:28:42 chen pptpd [6884]: GRE: read (fd = 6, buffer = 8059680, len = 8196) from PTY failed: status =-1 error = Input/output error, usually caused by unexpected termination of pppd, check option syntax and pppd logs

Dec 14 12:28:42 chen pptpd [6884]: CTRL: PTY read or GRE write failed (pty, gre) = (6, 7)

Dec 14 12:28:42 chen pptpd [6884]: CTRL: Client 192.168.102.108 control connection finished
I have already installed it several times. I don't know why it doesn't work. It's all done through the steps on the Internet ..
The error 628 is prompted during VPN dialing .. Always Prompt
Hope experts can help me to see it...