要求：网络互通（且每台路由都有一个虚拟接口）。每台路由上有一条浮动路由。
首先给两台PC配置同网段IP
VPCS[1]> ip 192.168.1.10 192.168.1.1
PC1 : 192.168.1.10 255.255.255.0 gateway 192.168.1.1
VPCS[1]> 2
VPCS[2]> ip 192.168.1.20 192.168.1.1
PC2 : 192.168.1.20 255.255.255.0 gateway 192.168.1.1
VPCS[2]> ping 192.168.1.10
192.168.1.10 icmp_seq=1 ttl=64 time=31.000 ms
192.168.1.10 icmp_seq=2 ttl=64 time=32.000 ms
192.168.1.10 icmp_seq=3 ttl=64 time=31.000 ms
192.168.1.10 icmp_seq=4 ttl=64 time=31.000 ms
192.168.1.10 icmp_seq=5 ttl=64 time=31.000 ms
给各个路由配IP和虚拟接口
R1
Interface IP-Address OK? Method Status Protocol
FastEthernet0/0 192.168.1.1 YES manual up up
FastEthernet0/1 12.0.0.1 YES manual up up
FastEthernet1/0 13.0.0.1 YES manual up up
Loopback0 1.1.1.1 YES manual up up
R2
Interface IP-Address OK? Method Status Protocol
FastEthernet0/0 12.0.0.2 YES manual up up
FastEthernet0/1 23.0.0.2 YES manual up up
Loopback0 2.2.2.2 YES manual up up
R3
Interface IP-Address OK? Method Status Pr otocol
FastEthernet0/0 23.0.0.3 YES manual up up
FastEthernet0/1 unassigned YES unset up up
Loopback0 3.3.3.3 YES manual up up
给每个路由做自身所不知道的静态路由
R1
ip route 2.2.2.0 255.255.255.0 12.0.0.2
ip route 2.2.2.0 255.255.255.0 13.0.0.3
ip route 3.3.3.0 255.255.255.0 12.0.0.2
ip route 3.3.3.0 255.255.255.0 13.0.0.3
ip route 23.0.0.0 255.255.255.0 12.0.0.2
ip route 23.0.0.0 255.255.255.0 13.0.0.3
R2
ip route 1.1.1.0 255.255.255.0 12.0.0.1
ip route 1.1.1.0 255.255.255.0 23.0.0.3
ip route 3.3.3.0 255.255.255.0 12.0.0.1
ip route 3.3.3.0 255.255.255.0 23.0.0.3
ip route 13.0.0.0 255.255.255.0 12.0.0.1
ip route 13.0.0.0 255.255.255.0 23.0.0.3
#ip route 192.168.1.0 255.255.255.0 12.0.0.1
R3
ip route 1.1.1.0 255.255.255.0 13.0.0.1
ip route 1.1.1.0 255.255.255.0 23.0.0.2
ip route 2.2.2.0 255.255.255.0 13.0.0.1
ip route 2.2.2.0 255.255.255.0 23.0.0.2
ip route 12.0.0.0 255.255.255.0 13.0.0.1
ip route 12.0.0.0 255.255.255.0 23.0.0.2
ip route 192.168.1.0 255.255.255.0 13.0.0.1
到达每个目标都有了两条路可以走，设浮动路由
R1(config)#ip route 3.3.3.0 255.255.255.0 12.0.0.2 10 (都类似)
最后检验：
VPCS[2]> ping 12.0.0.2
12.0.0.2 icmp_seq=1 ttl=254 time=125.000 ms
12.0.0.2 icmp_seq=2 ttl=254 time=93.000 ms
12.0.0.2 icmp_seq=3 ttl=254 time=94.000 ms
12.0.0.2 icmp_seq=4 ttl=254 time=78.000 ms
12.0.0.2 icmp_seq=5 ttl=254 time=94.000 ms
VPCS[2]> ping 2.2.2.2
2.2.2.2 icmp_seq=1 ttl=254 time=93.000 ms
2.2.2.2 icmp_seq=2 ttl=254 time=94.000 ms
2.2.2.2 icmp_seq=3 ttl=254 time=109.000 ms
2.2.2.2 icmp_seq=4 ttl=254 time=93.000 ms
2.2.2.2 icmp_seq=5 ttl=254 time=125.000 ms
【R1和R3也可作默认路由。。因为做过浮动路由后，只有一条路生效，所以可看做是单出口】