Virtual IP not functioning

Hi! Recently I’ve tried to create virtual IP at my mifi 3grouter.

ifconfig eth0:0 1.1.1.21 netmask 255.255.255.0 up

After creating the ip, i tried to ping the remote device and seems no response. When I use the remote device to ping to 1.1.1.21 and got reply.

Can I know is there any setting at mifi 3grouter? Thanks