ANS-C01 Multicast in AWS Practice Question
A company is migrating a legacy application to AWS. The application uses multicast for service discovery. Which AWS service or feature can be used to support multicast traffic within a VPC?
⚠ Common exam trap
Candidates often assume that Direct Connect or VPC Peering can support multicast because they handle general IP traffic, but AWS restricts multicast to Transit Gateway multicast domains only.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
AWS Transit Gateway with multicast domain
AWS Transit Gateway multicast domains (option B) is the only service that natively supports multicast traffic within a VPC. The other listed options do not support multicast: Direct Connect requires additional on-premises configuration and does not provide VPC-native multicast, VPC multicast groups are not a supported feature, Internet Gateway only handles unicast, and VPC Peering also only supports unicast. Therefore, the correct answer is B.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
AWS Direct Connect with multicast
Why it's wrong here
AWS Direct Connect does not natively support multicast within a VPC. While it can transport multicast if configured with on-premises, it is not a service or feature that directly supports multicast within the VPC.
- ✓
AWS Transit Gateway with multicast domain
Why this is correct
AWS Transit Gateway multicast domains provide native support for multicast traffic within a VPC, allowing service discovery traffic to be forwarded between VPCs or on-premises networks.
- ✗
VPC multicast groups using network interfaces
Why it's wrong here
VPC multicast groups are not natively supported in AWS. Multicast within a VPC must be enabled through Transit Gateway multicast domains, not through direct VPC network interfaces.
- ✗
Internet Gateway (IGW)
Why it's wrong here
Internet Gateway (IGW) only supports unicast traffic and cannot handle multicast.
- ✗
VPC Peering
Why it's wrong here
VPC Peering only supports unicast traffic and does not support multicast.
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Same concept, more angles
2 more ways this is tested on ANS-C01
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A company is migrating a legacy on-premises application to AWS. The application requires multicast traffic between instances within a VPC. The network engineer must design a solution that supports multicast without modifying the application. Which AWS service or feature should be used?
hard- ✓ A.AWS Transit Gateway with multicast domain.
- B.VPC peering connections between all instance subnets.
- C.Application Load Balancer with UDP listener.
- D.AWS Site-to-Site VPN connections with multicast routing enabled.
Why A: AWS Transit Gateway supports multicast through the creation of a multicast domain, which allows multicast traffic to flow between instances in different subnets within the same VPC or across attached VPCs without modifying the application. This is the only native AWS service that provides multicast forwarding, making it the correct choice for this requirement.
Variation 2. A company is migrating a legacy application to AWS. The application requires multicast traffic between EC2 instances in the same VPC. Which AWS service can support this requirement?
medium- A.AWS VPC Lattice
- B.Network Load Balancer (NLB)
- C.Application Load Balancer (ALB)
- D.Gateway Load Balancer (GWLB)
- ✓ E.AWS Transit Gateway multicast domain
Why E: AWS Transit Gateway multicast domains are the only native AWS service that supports multicast traffic between EC2 instances within a VPC. AWS VPC Lattice does not support multicast; it provides service-to-service connectivity using HTTP/HTTPS and TCP. NLB, ALB, and GWLB are load balancers that distribute traffic but do not support multicast.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This ANS-C01 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the ANS-C01 exam.