ifmip <ifname> {add | del} {ipv4 address [netmask]}

[root@sylixos:/root]# help ifmip          
net interface add / delete secondary IPv4 address.
NOTICE: a fake interface 'mi*' will be create / delete.
ifmip [ifname] [{add | del}] [ipv4 address [netmask]]
[root@sylixos:/root]# 

[root@sylixos: /root]# ifmip en3 add 192.168.100.2 255.255.0.0
[root@sylixos: /root]# ifconfig
mi6   Link encap: Ethernet Hwaddr: 00: 1b: 22: 56: 8d: 74
      Mif: en3 Ifidx: 7 DHCP: D4 D6 Spd: N/A
      inet addr: 192.168.100.2 netmask: 255.255.0.0
      gateway: 0.0.0.0 broadcast: 192.168.255.255
      UP BROADCAST MTU:1500 Mertic：1