A London-based stockbroking firm has set up multiple VPCs in eu-west-1 and eu-west-2 regions. Direct Connect is enabled from the head office to these regions. The firm now wants a new stock ticker application installed on EC2 instances in eu-west-1 and eu-west-2 regions. For this application to work properly a multicast needs to be enabled. Which of the following solution will meet this requirement most cost-effectively?

Answer options:

A.Create a VPN from an instance in eu-west-1 to the corporate office. Use existing Direct Connect connectivity from the corporate office to VPC in eu-west-2 Region.
B.Create a separate VPN at each region from the corporate office & allow communication between two instances over the corporate network.
C.Create an inter-region VPC peering between VPC in two different regions.
D.Create a software VPN between instances in two VPC in two different regions.

Correct Answer – D
To have multicast enabled between two EC2 instances within a VPC, a software VPN can have multicast communication between these two instances in different regions.
Options A & B are incorrect as This will create additional configuration changes & will allow all instances in Region eu-west-1 to communicate with region eu-west-2 unless control is set.
Option C is incorrect as although this will work this will allow all instances in each VPC to communicate with each other. Since only one instance needs to communicate with other instances, additional control needs to be done on routing / Security Groups.
 For more information on using software VPN appliances, refer to the following URL
https://aws.amazon.com/blogs/networking-and-content-delivery/integrating-external-multicast-services-with-aws/
https://aws.amazon.com/answers/networking/aws-multiple-region-multi-vpc-connectivity/