Installed loopback adaptor but could not connect CLOUD icon with routers, gave error about being unable to create generic ethernet NIO .
Need to reboot the PC after installing loopback adapter.
Consistent behavior on 2 different PC
After reboot was able to connect CLOUD to router and ping it.
Following post is quite helpful.
http://www.smartpctricks.com/2014/06/connecting-gns3-real-networks.html