浮动静态路由
1.将AR1、AR2、AR3、AR4的所有接口配置好ip地址和子网掩码
配置方法：
ip address IP地址 子网掩码2.配置AR1、AR2、AR3均可访问AR4的loopback0
1）在AR1上添加去往AR4的loopback0的路由
[AR1]ip route-static 10.4.0.4 32 10.1.2.2
2）在AR2上添加去往AR4的loopback0的路由
[AR2]ip route-static 10.4.0.4 32 Serial 4/0/0
3）在AR3上添加去往AR4的loopback0的路由
[AR3]ip route-static 10.4.0.4 32 10.2.3.2
4）添加返回的路由条目
[AR4]ip route-static 10.1.2.0 24 Serial 4/0/0
[AR4]ip route-static 10.2.3.0 24 Serial 4/0/0
5）测试连通性
在AR1上：
[AR1]ping 10.4.0.4
PING 10.4.0.4: 56 data bytes, press CTRL_C to break
Reply from 10.4.0.4: bytes=56 Sequence=1 ttl=254 time=30 ms
Reply from 10.4.0.4: bytes=56 Sequence=2 ttl=254 time=20 ms
Reply from 10.4.0.4: bytes=56 Sequence=3 ttl=254 time=30 ms
Reply from 10.4.0.4: bytes=56 Sequence=4 ttl=254 time=40 ms
Reply from 10.4.0.4: bytes=56 Sequence=5 ttl=254 time=30 ms
--- 10.4.0.4 ping statistics ---
5 packet(s) transmitted
5 packet(s) received
0.00% packet loss
round-trip min/avg/max = 20/30/40 ms
在AR3上：
[AR3]ping 10.4.0.4
PING 10.4.0.4: 56 data bytes, press CTRL_C to break
Reply from 10.4.0.4: bytes=56 Sequence=1 ttl=254 time=90 ms
Reply from 10.4.0.4: bytes=56 Sequence=2 ttl=254 time=30 ms
Reply from 10.4.0.4: bytes=56 Sequence=3 ttl=254 time=30 ms
Reply from 10.4.0.4: bytes=56 Sequence=4 ttl=254 time=40 ms
Reply from 10.4.0.4: bytes=56 Sequence=5 ttl=254 time=20 ms
--- 10.4.0.4 ping statistics ---
5 packet(s) transmitted
5 packet(s) received
0.00% packet loss
round-trip min/avg/max = 20/42/90 ms
3.配置浮动静态路由
1）关闭AR1与AR2之间的链路，然后再次查看连接性
[AR1]interface GigabitEthernet 0/0/0
[AR1-GigabitEthernet0/0/0]shutdown
再次测试连通性
[AR1]ping 10.4.0.4
PING 10.4.0.4: 56 data bytes, press CTRL_C to break
Request time out
Request time out
Request time out
Request time out
Request time out
--- 10.4.0.4 ping statistics ---
5 packet(s) transmitted
0 packet(s) received
100.00% packet loss
以上输出结果表示，当AR1的G0/0/0接口关闭后，AR1就也不能够再访问AR4了。但查看拓扑图，可以发现AR1其实可以通过把报文转发给AR3，然后再经过AR2转发给AR4。
4.配置浮动静态路由
1）配置一条AR1去往AR4的静态路由，将下一跳指向AR3，并将优先级设置为65。
[AR1]ip route-static 10.4.0.4 32 10.1.3.3 preference 65
2）查看这条路由信息
[AR1]display ip routing-table protocol static
AR1上已经成功添加了一条新的静态路由，并且该路由条目的优先级为65。同时，之前配置的指向AR2的静态路由，因为下一跳不可达的原因，已经处于不可用的状态了。
3）测试连通性
[AR1]ping 10.4.0.4
PING 10.4.0.4: 56 data bytes, press CTRL_C to break
Request time out
Request time out
Request time out
Request time out
Request time out
--- 10.4.0.4 ping statistics ---
5 packet(s) transmitted
0 packet(s) received
100.00% packet loss
以上输出结果表示AR1并不能ping通AR4连接的10.4.0.4网段。
不能通信的原因是：AR4及AR2都没有去往10.1.3.0/24网段的路由。因此，需要管理员在AR2和AR4上分别添加以下两条路由：
[AR2]ip route-static 10.1.3.0 24 10.2.3.3
[AR4]ip route-static 10.1.3.0 24 Serial 4/0/0
再次测试连通性
[AR1]ping 10.4.0.4
PING 10.4.0.4: 56 data bytes, press CTRL_C to break
Reply from 10.4.0.4: bytes=56 Sequence=1 ttl=253 time=30 ms
Reply from 10.4.0.4: bytes=56 Sequence=2 ttl=253 time=30 ms
Reply from 10.4.0.4: bytes=56 Sequence=3 ttl=253 time=40 ms
Reply from 10.4.0.4: bytes=56 Sequence=4 ttl=253 time=40 ms
Reply from 10.4.0.4: bytes=56 Sequence=5 ttl=253 time=30 ms
--- 10.4.0.4 ping statistics ---
5 packet(s) transmitted
5 packet(s) received
0.00% packet loss
round-trip min/avg/max = 30/34/40 ms
4.恢复AR1连接AR2之间的接口
[AR1]interface GigabitEthernet 0/0/0
[AR1-GigabitEthernet0/0/0]undo shutdown
查看当前路由表
当AR1连接AR2之间的链路恢复的时候，AR1重新选择AR2为最佳的下一跳。这是因为当同一条路由拥有二个下一跳的时候，路由器会通过比较它们的优先级来选择最优的下一跳：优先级越小，表示这条路由越优。同时，指向AR3为下一跳的路由，此时也变为了Inactive的状态。当主选链路失效的时候，这条沉下去的路由将会重新被启用。
