ip address 192.168.1.2 255.255.255.0 secondary    //模拟子网中第二台主机

!

interface Loopback2                                              //模拟子网二：192.168.2.0/24

ip address 192.168.2.1 255.255.255.0

ip address 192.168.2.2 255.255.255.0 secondary

!

interface FastEthernet0/0

ip address 12.0.0.1 255.255.255.0

duplex half