2.Static route 静态路由与最长匹配
R1
int E0/0/0
ip add 192.168.1.1 255.255.255.0
R2
int E0/0/0
ip add 192.168.1.2 24
ip route-s 192.168.1.1 255.255.255.0 NULL0  //Null 0为逻辑接口，数据包到达此接口即丢弃。

 

[R2]dis cur | in route
ospf 10 router-id 2.2.2.2
ip route-static 192.168.1.1 255.255.255.255 NULL0


[R2] dis ip rou
Route Flags: R - relay, D - download to fib
------------------------------------------------------------------------------
Routing Tables: Public
         Destinations : 6        Routes : 6       

Destination/Mask    Proto   Pre  Cost      Flags NextHop         Interface

        2.2.2.2/32  Direct  0    0           D   127.0.0.1       LoopBack0
      127.0.0.0/8   Direct  0    0           D   127.0.0.1       InLoopBack0
      127.0.0.1/32  Direct  0    0           D   127.0.0.1       InLoopBack0
    192.168.1.0/24  Direct  0    0           D   192.168.1.2     Ethernet0/0/0
    192.168.1.1/32  Static   60   0           D   0.0.0.0         NULL0
    192.168.1.2/32  Direct  0    0           D   127.0.0.1       Ethernet0/0/0

         路由选路时，会遵循最长匹配原则，此静态路由为32位为最长匹配。导致数据包被发送到Null0接口，进而丢弃。

[R2]ping 192.168.1.1
  PING 192.168.1.1: 56  data bytes, press CTRL_C to break
    Request time out
    Request time out
    Request time out
    Request time out
    Request time out

  --- 192.168.1.1 ping statistics ---
    5 packet(s) transmitted
    0 packet(s) received
    100.00% packet loss
    百分之百丢包率，无法ping通。