Thanks for the reply, i checked the firewall rules, VMs can ping outside to the same network ie to the another VM's in the provider network. I followed the example configuration given in this document. https://docs.openstack.org/newton/install-guide-ubuntu/launch-instance-networks-selfservice.html (https://docs.openstack.org/newton/ins...)

Could you attach the network topology screenshot from horizon? And also mention the details of your external network

Here is the network topology screen shot [https://ibb.co/fHw00k] My external network details Network Address: 192.168.7.0/24 Gateway: 192.168.7.100

Add a router that connects your internal network to the external network. First check if you are able to ping the router gateway from the VM. Second, associate a floating IP to your VM instance, 3rd associate security group rule to allow ssh, icmp (ping is disabled by default) with your VM instance.

Yes the virtual router is added and the security rules have been set. Its not the problem, that the controller cannot ping the VM instance, instead VM cannot ping the the controller. Controller can ping the floating ip of the VM and the selfservice network IP through the sudo ip netns exec command.