问题：
在一台centos系统的vps上自己搭建了一个pptp协议的vpn服务，搭建教程参考这个：
http://www.4linuxfun.com/structures-unde...
之前搭建完之后正常使用了很久，最近几个月突然发现连不上了，表现是连上之后过一会儿就断开
然后重新按照步骤又重新安装了一次，无效。
报错log如下：
Apr 8 00:10:19 server1 pptpd[28175]: CTRL: Client 101.81.75.75 control connection started
Apr 8 00:10:20 server1 pptpd[28175]: CTRL: Starting call (launching pppd, opening GRE)
Apr 8 00:10:20 server1 pppd[28191]: pppd 2.4.5 started by root, uid 0
Apr 8 00:10:20 server1 pppd[28191]: Using interface ppp0
Apr 8 00:10:20 server1 pppd[28191]: Connect: ppp0 <--> /dev/pts/1
Apr 8 00:10:20 server1 pptpd[28175]: discarding duplicate packet 1
Apr 8 00:10:28 server1 pppd[28191]: Cannot determine ethernet address for proxy ARP
Apr 8 00:10:28 server1 pppd[28191]: local IP address 172.16.36.1
Apr 8 00:10:28 server1 pppd[28191]: remote IP address 172.16.36.2
Apr 8 00:10:39 server1 pptpd[28175]: GRE: read(fd=7,buffer=6097c0,len=8260) from network failed: status = -1 error = Message too long
Apr 8 00:10:39 server1 pptpd[28175]: CTRL: GRE read or PTY write failed (gre,pty)=(7,6)
Apr 8 00:10:39 server1 pppd[28191]: Modem hangup
Apr 8 00:10:39 server1 pppd[28191]: Connect time 0.2 minutes.
Apr 8 00:10:39 server1 pppd[28191]: Sent 74166 bytes, received 28427 bytes.
Apr 8 00:10:39 server1 pppd[28191]: Connection terminated.
Apr 8 00:10:39 server1 pppd[28191]: Exit.
Apr 8 00:10:39 server1 pptpd[28175]: CTRL: Client 101.81.75.75 control connection finished我的其他配置：
# /etc/pptpd.conf
logwtmp
pidfile /var/log/pptpd.pid
connections 253
option /etc/ppp/options.pptpd
localip 172.16.36.1
remoteip 172.16.36.2-254# /etc/ppp/options.pptpd
name pptpd
+chap
refuse-pap
refuse-chap
refuse-mschap
require-mschap-v2
ms-dns 8.8.8.8
ms-dns 8.8.4.4
proxyarp
lock
nobsdcomp
novj
novjccomp
nologfd
nodeflate# /etc/sysctl.conf
net.ipv4.ip_forward = 1
net.bridge.bridge-nf-call-ip6tables = 0
net.bridge.bridge-nf-call-iptables = 0
net.bridge.bridge-nf-call-arptables = 0# /etc/sysconfig/iptables
*raw
:PREROUTING ACCEPT [616950:278743073]
:OUTPUT ACCEPT [350332:306920807]
COMMIT
*nat
:PREROUTING ACCEPT [26337:1763769]
:POSTROUTING ACCEPT [6572:497642]
:OUTPUT ACCEPT [6572:497642]
-A POSTROUTING -s 172.16.36.0/24 -j SNAT --to-source 209.141.40.204
-A POSTROUTING -s 172.16.36.0/24 -o venet0 -j MASQUERADE
-A POSTROUTING -s 172.16.36.0/24 -o eth0 -j MASQUERADE
COMMIT
*mangle
:PREROUTING ACCEPT [616950:278743073]
:INPUT ACCEPT [259936:30860825]
:FORWARD ACCEPT [356739:247840854]
:OUTPUT ACCEPT [350332:306920807]
:POSTROUTING ACCEPT [705693:554538780]
COMMIT
*filter
:INPUT ACCEPT [83:5911]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [55:4327]
COMMIT可能是你的运营商IP路由的问题，试着重启下VPS和VPS的网络
service network restart
对应的网卡也试着重启下
有人来回答么。。。。