1.关于×××中的768: 因为加密数据失败连接尝试失败.
解决方法：
“运行”“services.msc”然后在服务中启用“IPSEC services”即可，如为了方便以后经常使用L2TP IPsec ×××，则可以把该项服务设置为“自动”。
以下是原文：
Error 768 corresponds to Policy mismatch between client and server. Make
sure IPSec service is running on both client as well as the server. You can
do this by typing this command on command prompt "sc query policyagent" if
this returns "Stopped" then to start this service type "net start
policyagent".
sure IPSec service is running on both client as well as the server. You can
do this by typing this command on command prompt "sc query policyagent" if
this returns "Stopped" then to start this service type "net start
policyagent".
