AWS Certified Advanced Networking – Specialty (ANS-C01)Network DesignMedium
A company is migrating a legacy application to AWS that relies on multicast for service discovery and inter-instance communication. The application will be deployed across several subnets within a single VPC. How can multicast traffic be supported in this AWS environment?
- AConfigure a VPC Peering connection between subnets to enable multicast.
- BUtilize AWS Transit Gateway with multicast domains.
- CDeploy a custom routing appliance within the VPC to forward multicast traffic.
- DEnable multicast directly on the VPC route tables.
Show answer & explanationAnswer & explanation
Correct answer: B. Utilize AWS Transit Gateway with multicast domains.
AWS Transit Gateway supports multicast, allowing multicast traffic to be routed between subnets within a VPC and even across VPCs attached to the same Transit Gateway. You create multicast domains to define the scope of multicast traffic, which is essential for legacy applications relying on this protocol.
Why the other options are wrong
- A. VPC Peering does not support multicast traffic; it's point-to-point unicast.
- C. While technically possible, deploying and managing custom routing appliances for multicast is complex, unscalable, and not an AWS-native solution.
- D. VPC route tables and the underlying network infrastructure do not natively support multicast routing without a service like Transit Gateway.
Transit Gateway Multicast
AWS Transit Gateway provides native support for IP multicast, allowing you to build multicast groups and route multicast traffic within and across VPCs.
- Supports legacy applications requiring multicast
- Routes multicast traffic within and across VPCs
- Uses multicast domains for scope definition
- Scalable and managed service
Memory trick: TGW broadcasts your legacy app's messages.