MSR2660-XS l2tp隧道异常

用我们设备替换华为设备做LNS，对端设备是LAC地址172.20.A.A/32。

0口是上行，地址192.168.B.B/29。地址池和终端密码做在我们这端。终端属于用4G卡拨号。

隧道和接口会建立起来一段时间后中断：

1、在PPPoE协商过程中，PPP协商阶段，接口和隧道是会UP的，协商失败后就Down了，这个是正常现象：

2、分析debug过程：

*Jan  1 12:00:11:560 2021 Device PPP/7/FSM_PACKET_1: 

  PPP Packet: 

      Virtual-Access0 Output LCP(c021) Packet, PktLen 19 

      Current State reqsent, code ConfReq(01), id d7, len 15 

      AuthProto(3), len 5, CHAP c2 23 05 

      MagicNumber(5), len 6, val cf cc a6 13 

*Jan  1 12:00:11:560 2021 Device PPP/7/EXTERNAL_EVENT_1: 

  PPP External Event: 

      Virtual-Access0: PPP l2tp prenego end!

*Jan  1 12:00:11:561 2021 Device L2TPV2/7/FWDDUMP: 

 Received a packet from PPP on interface Virtual-Access0 (length=19):

ff 03 c0 21 01 d7 00 0f 03 05 c2 23 05 05 06 c* c* a* 1*

*Jan  1 12:00:11:561 2021 Device L2TPV2/7/FWDDATA-PKT: 

 Encapsulated an L2TP data packet on interface Virtual-Access0 (length=53):

  Source IP: 192.168.B.B

  Destination IP: 172.20.A.A

  Source port: 1701

  Destination port: 1701

  Tunnel ID: 25852

  Session ID: 1

*Jan  1 12:00:11:661 2021 Device PPP/7/FWD_EXTERNAL_EVENT: 

  PPP External Event: 

      Virtual-Access0 deliver packet to worker[1] of user space success

*Jan  1 12:00:11:661 2021 Device PPP/7/FSM_PACKET_1: 

  PPP Packet: 

      Virtual-Access0 Input LCP(c021) Packet, PktLen 12 

      Current State reqsent, code ConfReq(01), id 0, len 8 

      MRU(1), len 4, val 05 dc 

*Jan  1 12:00:11:661 2021 Device PPP/7/FSM_EVENT_1: 

  PPP Event: 

      Virtual-Access0 LCP RCR+(Receive Config Good Request) Event 

      State reqsent 

*Jan  1 12:00:11:661 2021 Device PPP/7/FSM_PACKET_1: 

  PPP Packet: 

      Virtual-Access0 Output LCP(c021) Packet, PktLen 12 

      Current State reqsent, code ConfAck(02), id 0, len 8 

      MRU(1), len 4, val 05 dc 

*Jan  1 12:00:11:661 2021 Device PPP/7/FWD_EXTERNAL_EVENT: 

  PPP External Event: 

      Virtual-Access0 deliver packet to worker[1] of user space success

*Jan  1 12:00:11:661 2021 Device PPP/7/FSM_STATE_1: 

  PPP State Change: 

      Virtual-Access0 LCP: reqsent --> acksent 

*Jan  1 12:00:11:661 2021 Device PPP/7/FSM_PACKET_1: 

  PPP Packet: 

      Virtual-Access0 Input LCP(c021) Packet, PktLen 19 

      Current State acksent, code ConfRej(04), id d7, len 15 

      AuthProto(3), len 5, CHAP c2 23 05 

      MagicNumber(5), len 6, val cf cc a6 13

看debug是对端拒绝了CHAP，怀疑是CHAP的协商问题，可以改成PAP试试

两端都加上PAP测试，正常建立

ppp authentication-mode chap pap