错误日志查看:

cat /var/log/syslog | tail -30

记录:

Jun 16 23:32:55 iZ6295lam1oZ kernel: [186586.171765] [UFW BLOCK] IN=eth1 OUT= MAC=00:16:3e:00:2d:8e:e4:c7:22:62:15:c1:08:00 SRC=223.104.5.230 DST=58.96.188.40 LEN=60 TOS=0x00 PREC=0x00 TTL=238 ID=47237 PROTO=47 
Jun 16 23:32:55 iZ6295lam1oZ kernel: [186586.223732] [UFW BLOCK] IN=eth1 OUT= MAC=00:16:3e:00:2d:8e:e4:c7:22:62:15:c1:08:00 SRC=223.104.5.230 DST=58.96.188.40 LEN=65 TOS=0x00 PREC=0x00 TTL=238 ID=63815 PROTO=47 
Jun 16 23:32:58 iZ6295lam1oZ kernel: [186589.172931] [UFW BLOCK] IN=eth1 OUT= MAC=00:16:3e:00:2d:8e:e4:c7:22:62:15:c1:08:00 SRC=223.104.5.230 DST=58.96.188.40 LEN=60 TOS=0x00 PREC=0x00 TTL=238 ID=3407 PROTO=47 
Jun 16 23:32:58 iZ6295lam1oZ kernel: [186589.178289] [UFW BLOCK] IN=eth1 OUT= MAC=00:16:3e:00:2d:8e:e4:c7:22:62:15:c1:08:00 SRC=223.104.5.230 DST=58.96.188.40 LEN=65 TOS=0x00 PREC=0x00 TTL=238 ID=42738 PROTO=47 
Jun 16 23:33:01 iZ6295lam1oZ pppd[16686]: LCP: timeout sending Config-Requests
Jun 16 23:33:01 iZ6295lam1oZ pppd[16686]: Connection terminated.
Jun 16 23:33:01 iZ6295lam1oZ pppd[16686]: Modem hangup
Jun 16 23:33:01 iZ6295lam1oZ pppd[16686]: Exit.
Jun 16 23:33:01 iZ6295lam1oZ pptpd[16685]: GRE: read(fd=6,buffer=7fe41e92b4a0,len=8196) from PTY failed: status = -1 error = Input/output error, usually caused by unexpected termination of pppd, check option syntax and pppd logs
Jun 16 23:33:01 iZ6295lam1oZ pptpd[16685]: CTRL: PTY read or GRE write failed (pty,gre)=(6,7)
Jun 16 23:33:01 iZ6295lam1oZ pptpd[16685]: CTRL: Reaping child PPP[16686]
Jun 16 23:33:01 iZ6295lam1oZ pptpd[16685]: CTRL: Client 223.104.5.230 control connection finished

可能解决方法:

1),防火墙允许1723和47端口,把53端口也加上
2),加载iptables中的几个模块:ip_nat_pptp ,ip_nat_proto_gre,ip_conntrack_pptp

~#: modprobe ip_nat_pptp
~#: modprobe ip_nat_proto_gre[可能提示找不到,没关系,执行一遍以防万一]
~#: modprobe ip_conntrack_pptp

查看模块是否加载

root@ubuntu:/etc/iptables# lsmod |grep pptp
nf_nat_pptp 2245 0 
nf_conntrack_pptp 5549 1 nf_nat_pptp
nf_conntrack_proto_gre 4734 1 nf_conntrack_pptp
nf_nat_proto_gre 1719 1 nf_nat_pptp
nf_nat 19286 3 nf_nat_pptp,nf_nat_proto_gre,iptable_nat
nf_conntrack 73326 7 nf_nat_pptp,nf_conntrack_pptp,nf_conntrack_proto_gre,xt_state,iptable_nat,nf_nat,nf_conntrack_ipv4

然后重启pptpd服务,就好了。

/etc/init.d/pptpd restart

end.