关于MSR G2路由器和中兴路由器通过ppp mp对接

问题现象：

MSR G2路由器与中兴路由器在做PPP MP 对接的时候，出现PPP MP工作不正常，MP-group、Serial口不断UP DOWN的现象。将接口的mp取消，则接口物理和协议都能正常up。

告警信息：

Log日志信息：

37%Sep  7 10:21:05:136 2015 220zhongdiantou-MSR36-40-R1 IFNET/5/LINK_UPDOWN: Line protocol state on the interface Serial7/0 changed to up.
%@38%Sep  7 10:21:05:138 2015 220zhongdiantou-MSR36-40-R1 IFNET/3/PHY_UPDOWN: Physical state on the interface MP-group0 changed to up.
%@39%Sep  7 10:21:05:138 2015 220zhongdiantou-MSR36-40-R1 IFNET/5/LINK_UPDOWN: Line protocol state on the interface MP-group0 changed to up.
%@40%Sep  7 10:21:05:156 2015 220zhongdiantou-MSR36-40-R1 IFNET/5/LINK_UPDOWN: Line protocol state on the interface Serial7/0 changed to down.
%@41%Sep  7 10:21:05:159 2015 220zhongdiantou-MSR36-40-R1 IFNET/3/PHY_UPDOWN: Physical state on the interface MP-group0 changed to down.
%@42%Sep  7 10:21:05:160 2015 220zhongdiantou-MSR36-40-R1 IFNET/5/LINK_UPDOWN: Line protocol state on the interface MP-group0 changed to down.
%@43%Sep  7 10:21:08:349 2015 220zhongdiantou-MSR36-40-R1 IFNET/5/LINK_UPDOWN: Line protocol state on the interface Serial7/1 changed to up.
%@44%Sep  7 10:21:08:351 2015 220zhongdiantou-MSR36-40-R1 IFNET/3/PHY_UPDOWN: Physical state on the interface MP-group1 changed to up.
%@45%Sep  7 10:21:08:351 2015 220zhongdiantou-MSR36-40-R1 IFNET/5/LINK_UPDOWN: Line protocol state on the interface MP-group1 changed to up.

设备debug信息：

*Sep  7 12:48:37:635 2015 220zhongdiantou-MSR36-40-R1 PPP/7/FSM_STATE_0:

  PPP State Change:

      Serial7/1 LCP: stopped --> acksent

*Sep  7 12:48:37:637 2015 220zhongdiantou-MSR36-40-R1 PPP/7/EXTERNAL_EVENT:

  PPP External Event:

      Serial7/1 deliver packet to user space success

*Sep  7 12:48:37:637 2015 220zhongdiantou-MSR36-40-R1 PPP/7/FSM_PACKET_0:

  PPP Packet:

      Serial7/1 Input LCP(c021) Packet, PktLen 30

      Current State acksent, code ConfAck(02), id ff, len 26

      MagicNumber(5), len 6, val dc fd e8 86

      MRRU(11), len 4, val 05 dc

      Discri(13), len c, val 01 4d 50 2d 67 72 6f 75 70 31

%Sep  7 12:48:37:642 2015 220zhongdiantou-MSR36-40-R1 IFNET/5/LINK_UPDOWN: Line protocol state on the interface Serial7/1 changed to up.

*Sep  7 12:48:37:637 2015 220zhongdiantou-MSR36-40-R1 PPP/7/FSM_EVENT_0:

  PPP Event:

      Serial7/1 LCP RCA(Receive Config Ack) Event

      State acksent

*Sep  7 12:48:37:638 2015 220zhongdiantou-MSR36-40-R1 PPP/7/FSM_STATE_0:

  PPP State Change:

      Serial7/1 LCP: acksent --> opened

%Sep  7 12:48:37:643 2015 220zhongdiantou-MSR36-40-R1 IFNET/3/PHY_UPDOWN: Physical state on the interface MP-group1 changed to up.

%Sep  7 12:48:37:643 2015 220zhongdiantou-MSR36-40-R1 IFNET/5/LINK_UPDOWN: Line protocol state on the interface MP-group1 changed to up.

*Sep  7 12:48:37:659 2015 220zhongdiantou-MSR36-40-R1 PPP/7/EXTERNAL_EVENT:

  PPP External Event:

      Serial7/1 deliver packet to user space success

*Sep  7 12:48:37:659 2015 220zhongdiantou-MSR36-40-R1 PPP/7/FSM_PACKET_0:

  PPP Packet:

      Serial7/1 Input LCP(c021) Packet, PktLen 8

      Current State opened, code TermReq(05), id ac, len 4               //前面协商均正常，此处突然收到对端发送过来的terminal终止协商报文，导致协商终端PPP down。

原因分析：

当使用MP-Group进行MP捆绑，缺省情况下，MSR G2路由器发送报文中的终端描述符（Endpoint）为设备配置的MP-Group组名称。

中兴对MP的捆绑实现可能存在如下的限制：同一路由器下多个Multilink口对应的对端终端描述符不能重复，如果重复，会将后面捆绑的链路断开。因此当有两个或两个以上MSR设备与中兴路由器通过PPP-MP互联，且配置的MP-Group组名称相同时，由于发送给中兴的终端描述符是相同的，这种情况下中兴路由器会将链路拆链。

解决办法：

通过命令ppp mp endpoint  xxx 为MP-Group组配置不同的终端描述符