Comment 5 for bug 1153626

I'm in a similar situation: An ec2 instance with just one network interface, to which I have assigned a secondary IP address.

This bit from the AWS docs is interesting:

"If you are using Amazon Linux, the ec2-net-utils package can take care of this step for you. It configures additional network interfaces that you attach while the instance is running, refreshes secondary IP addresses during DHCP lease renewal, and updates the related routing rules."

http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/using-instance-addressing.html#StepTwoConfigOS

Perhaps it would be worthwhile for cloud-init to do the same thing that Amazon's ec2-net-utils package does.