(1) open VPN Client help files check corresponding fault log,unsuccessful
(2)open VPN Client debug tools,choose all of options,check debug log
Found fault:[IOuter]<SOCK_T_ReceiveMsg>: recvfrom error
No corresponding help
(3)open Wireshark,set capture filter host is LNS address
From captured message know opposite did not open L2TP
(4)contact administrators found LNS address wrong,use changed LNS address,connect normal