Overlay networks on AWS

Software Defined Networks (SDN) are all the rage and for good reason.  A couple of very good reasons when running on AWS are:
1. Supporting multi-cast on AWS which does not natively support multi-cast
2. Dealing with network address overlapping when using AWS VPC

There are a number of alternatives.  https://code.google.com/p/openpgm/
This is one that is certified to run on AWS:
http://www.cohesiveft.com/products/vns3

Here is a very comprehensive post on multicast on AWS:

 https://www.buckhill.co.uk/blog/how-to-enable-broadcast-and-multicast-on-amazon-aws-ec2/2#.VZP_MbzI-lO