I have a basic DevStack setup. I am using Ubuntu cloud images. The machine on which I have DevStack set up is having internet connectivity. But when I log into an instance and run apt-get update, it came to my fore that the instance do not have internet connectivity. Am I missing a step to allow access to the VM? What exactly is that step?
PS: I have assigned a floating IP to the instance. That is all I have done so far.
Does ifconfig return the correct IPs?
If everything is fine, try checking your system's routing status by route. Your Linux may have chosen a wrong default gateway for you.
See http://www.cyberciti.biz/faq/linux-setup-default-gateway-with-route-command/