MSR V7平台路由器静态路由与BFD联动（非直连）不生效

组网如下：

RTA和RTC之间配置到对端LOOPBACK接口的静态路由，并且该静态路由与BFD联动，当BFD失效后，对应的静态路由也要生效。

配置完成后，发现BFD session是down的。

RTA与RTC上，BFD会话都是down的

[RTA]display current-configuration | include route-static
      ip route-static 123.1.1.2 32 10.1.1.2 bfd control-packet bfd-source 10.1.1.1

[RTA]display bfd session verbose
     Total Session Num: 1     Up Session Num: 0     Init Mode: Active

 IPv4 Session Working Under Ctrl Mode:
       Local Discr: 1537                 Remote Discr: 0
         Source IP: 10.1.1.1           Destination IP: 10.1.1.2
     Session State: Down                    Interface: N/A
      Min Tx Inter: 1000ms               Act Tx Inter: 1000ms
      Min Rx Inter: 1000ms               Detect Inter: 5000ms
          Rx Count: 0                        Tx Count: 178
      Connect Type: Indirect           Running Up for: 00:00:00
         Hold Time: 0ms                     Auth mode: None
       Detect Mode: Async                        Slot: 0
          Protocol: STATIC
           Version: 1
         Diag Info: No Diagnostic
        
        
        
    [RTC]display current-configuration | include route-static
      ip route-static 123.1.1.1 32 20.1.1.2 bfd control-packet bfd-source 20.1.1.1

[RTC]display bfd session verbose
     Total Session Num: 1     Up Session Num: 0     Init Mode: Active

 IPv4 Session Working Under Ctrl Mode:
       Local Discr: 1537                 Remote Discr: 0
         Source IP: 20.1.1.1           Destination IP: 20.1.1.2
     Session State: Down                    Interface: N/A
      Min Tx Inter: 1000ms               Act Tx Inter: 1000ms
      Min Rx Inter: 1000ms               Detect Inter: 5000ms
          Rx Count: 0                        Tx Count: 98
      Connect Type: Indirect           Running Up for: 00:00:00
         Hold Time: 0ms                     Auth mode: None
       Detect Mode: Async                        Slot: 0
          Protocol: STATIC
           Version: 1
         Diag Info: No Diagnostic

通过在设备上debug发现，BFD控制报文的目的地址并非是BFD对端设备的IP地址。
*Jan 27 11:59:15:617 2016 RTC BFD/7/DEBUG: Send:Ctrl packet, Src:20.1.1.1, Dst:20.1.1.2, Ver:1, Diag:0, Sta:1 P/F/C/A/D/M:0/0/1/0/0/0, Mult:5 LD/RD:1537/0, Tx:1000ms, Rx:1000ms, EchoRx:1000ms

因此，BFD对端设备收不到本端发送的BFD控制报文，BFD会话就是down的。

修改静态路由的下一跳为BFD对端设备的IP地址，BFD会话up，问题解决。

[RTA]display current-configuration | include route-static
      ip route-static 123.1.1.2 32 10.1.1.2 bfd control-packet bfd-source 10.1.1.1

修改为ip route-static 123.1.1.2 32 20.1.1.1 bfd control-packet bfd-source 10.1.1.1

[RTC]display current-configuration | include route-static
      ip route-static 123.1.1.1 32 20.1.1.2 bfd control-packet bfd-source 20.1.1.1

修改为ip route-static 123.1.1.1 32 10.1.1.1 bfd control-packet bfd-source 20.1.1.1

静态路由的下一跳，就是BFD控制报文的目的地址，因此下一跳地址必须配置到BFD对端设备上，且两端设备的静态路由的下一跳和BFD源地址必须互为镜像。

比如本例中RTA中静态路由下一跳为RTC静态路由的BFD源地址，RTA中静态路由的源地址为RTC静态路由的下一跳。