我很困惑，VPN 客户端在我的虚拟机上运行完美，今天我尝试连接 L2TP VPN 服务器时却失败了……这是我的客户端虚拟机的日志，有人能帮忙吗？我没有做任何更改（故意的），我不明白为什么对端突然不想进行身份验证，这是过去预料到的还是新情况？我的平板电脑仍然可以像以前一样连接。
Sep 4 22:29:51 ubuntu64 ipsec_setup: ...Openswan IPsec started
Sep 4 22:29:51 ubuntu64 L2tpIPsecVpnControlDaemon: Command ipsec setup start finished with exit code 0
Sep 4 22:29:51 ubuntu64 L2tpIPsecVpnControlDaemon: Executing command service xl2tpd start
Sep 4 22:29:51 ubuntu64 xl2tpd[4665]: setsockopt recvref[30]: Protocol not available
Sep 4 22:29:51 ubuntu64 ipsec__plutorun: adjusting ipsec.d to /etc/ipsec.d
Sep 4 22:29:51 ubuntu64 xl2tpd[4665]: This binary does not support kernel L2TP.
Sep 4 22:29:51 ubuntu64 L2tpIPsecVpnControlDaemon: Command service xl2tpd start finished with exit code 0
Sep 4 22:29:51 ubuntu64 pluto: adjusting ipsec.d to /etc/ipsec.d
Sep 4 22:29:51 ubuntu64 xl2tpd[4666]: xl2tpd version xl2tpd-1.3.6 started on ubuntu64 PID:4666
Sep 4 22:29:51 ubuntu64 xl2tpd[4666]: Written by Mark Spencer, Copyright (C) 1998, Adtran, Inc.
Sep 4 22:29:51 ubuntu64 xl2tpd[4666]: Forked by Scott Balmos and David Stipp, (C) 2001
Sep 4 22:29:51 ubuntu64 xl2tpd[4666]: Inherited by Jeff McAdams, (C) 2002
Sep 4 22:29:51 ubuntu64 xl2tpd[4666]: Forked again by Xelerance (www.xelerance.com) (C) 2006
Sep 4 22:29:51 ubuntu64 xl2tpd[4666]: Listening on IP address 0.0.0.0, port 1701
Sep 4 22:29:51 ubuntu64 ipsec__plutorun: 002 added connection description "CBER_L2TP_CABLE"
Sep 4 22:29:51 ubuntu64 L2tpIPsecVpnControlDaemon: Executing command ipsec auto --ready
Sep 4 22:29:52 ubuntu64 ipsec__plutorun: 002 added connection description "CBER_L2TP_ADSL"
Sep 4 22:29:52 ubuntu64 L2tpIPsecVpnControlDaemon: Command ipsec auto --ready finished with exit code 0
Sep 4 22:29:52 ubuntu64 L2tpIPsecVpnControlDaemon: Executing command ipsec auto --up CBER_L2TP_CABLE
Sep 4 22:29:52 ubuntu64 L2tpIPsecVpnControlDaemon: Command ipsec auto --up CBER_L2TP_CABLE finished with exit code 0
Sep 4 22:29:53 ubuntu64 L2tpIPsecVpnControlDaemon: Closing client connection
Sep 4 22:29:53 ubuntu64 xl2tpd[4666]: Connecting to host yin-cable.dyndns.biz, port 1701
Sep 4 22:29:55 ubuntu64 xl2tpd[4666]: Connection established to 999.999.999.999, 1701. Local: 19801, Remote: 56042 (ref=0/0).
Sep 4 22:29:55 ubuntu64 xl2tpd[4666]: Calling on tunnel 19801
Sep 4 22:29:55 ubuntu64 xl2tpd[4666]: check_control: Received out of order control packet on tunnel 56042 (got 0, expected 1)
Sep 4 22:29:55 ubuntu64 xl2tpd[4666]: handle_packet: bad control packet!
Sep 4 22:29:55 ubuntu64 xl2tpd[4666]: check_control: Received out of order control packet on tunnel 56042 (got 0, expected 1)
Sep 4 22:29:55 ubuntu64 xl2tpd[4666]: handle_packet: bad control packet!
Sep 4 22:29:55 ubuntu64 xl2tpd[4666]: Call established with 999.999.999.999, Local: 5753, Remote: 13038, Serial: 1 (ref=0/0)
Sep 4 22:29:55 ubuntu64 xl2tpd[4666]: start_pppd: I'm running:
Sep 4 22:29:55 ubuntu64 xl2tpd[4666]: "/usr/sbin/pppd"
Sep 4 22:29:55 ubuntu64 xl2tpd[4666]: "passive"
Sep 4 22:29:55 ubuntu64 xl2tpd[4666]: "nodetach"
Sep 4 22:29:55 ubuntu64 xl2tpd[4666]: ":"
Sep 4 22:29:55 ubuntu64 xl2tpd[4666]: "file"
Sep 4 22:29:55 ubuntu64 xl2tpd[4666]: "/etc/ppp/CBER_L2TP_CABLE.options.xl2tpd"
Sep 4 22:29:55 ubuntu64 xl2tpd[4666]: "/dev/pts/4"
Sep 4 22:29:55 ubuntu64 pppd[4725]: Plugin passprompt.so loaded.
Sep 4 22:29:55 ubuntu64 pppd[4725]: pppd 2.4.5 started by root, uid 0
Sep 4 22:29:55 ubuntu64 pppd[4725]: Using interface ppp0
Sep 4 22:29:55 ubuntu64 pppd[4725]: Connect: ppp0 <--> /dev/pts/4
Sep 4 22:29:55 ubuntu64 NetworkManager[794]: SCPlugin-Ifupdown: devices added (path: /sys/devices/virtual/net/ppp0, iface: ppp0)
Sep 4 22:29:55 ubuntu64 NetworkManager[794]: SCPlugin-Ifupdown: device added (path: /sys/devices/virtual/net/ppp0, iface: ppp0): no ifupdown configuration found.
Sep 4 22:29:55 ubuntu64 NetworkManager[794]: <warn> /sys/devices/virtual/net/ppp0: couldn't determine device driver; ignoring...
Sep 4 22:29:55 ubuntu64 pppd[4725]: LCP terminated by peer (peer refused to authenticate)
Sep 4 22:29:55 ubuntu64 xl2tpd[4666]: control_finish: Connection closed to 999.999.999.999, serial 1 ()
Sep 4 22:29:55 ubuntu64 xl2tpd[4666]: Terminating pppd: sending TERM signal to pid 4725
Sep 4 22:29:55 ubuntu64 pppd[4725]: Terminating on signal 15
Sep 4 22:29:55 ubuntu64 pppd[4725]: Modem hangup
Sep 4 22:29:55 ubuntu64 pppd[4725]: Connection terminated.
Sep 4 22:29:55 ubuntu64 NetworkManager[794]: SCPlugin-Ifupdown: devices removed (path: /sys/devices/virtual/net/ppp0, iface: ppp0)
Sep 4 22:29:55 ubuntu64 pppd[4725]: Exit.
答案1
您的 L2TP 客户端在连接过程中丢失了您的密码。您必须将其添加到您的连接参数文件中，例如下面的用户名短语 - 密码“Your_pass”。
nano /etc/ppp/Your_connection_name.options.xl2tpd
并且您应该在文件底部添加：
password "Your_pass"
但要记住：
- 保留纯文本密码并不是一个好主意，
- 更改设置后，您的密码将被覆盖并消失。