How to Encrypt Traffic Between Application Load Balancer and EC2 Instances
A company wants to encrypt all data in transit between an Application Load Balancer (ALB) and its target EC2 instances. Which TWO actions should be taken?
Quick Answer
The correct answer is to configure the ALB listener to use HTTPS and set the target group protocol to HTTPS. This works because the listener terminates the client’s SSL connection, while the target group’s HTTPS protocol re-encrypts traffic between the ALB and EC2 instances, ensuring end-to-end encryption in transit. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this tests your understanding of how Application Load Balancers handle encryption at both the listener and target group layers, a common trap being that security group rules or listener rules alone can encrypt traffic—they cannot, as encryption is a protocol-level function, not a filtering one. A useful memory tip is to think of the ALB as a two-door system: the front door (listener) handles client encryption, and the back door (target group) handles server encryption; both must use HTTPS for the full path to be secure.
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
✓
Configure the target group to use HTTPS as the protocol
To encrypt data in transit between an Application Load Balancer (ALB) and its target EC2 instances, only the target group protocol needs to be configured to use HTTPS (Option B). The ALB listener protocol (HTTPS) encrypts traffic between the client and the ALB, not between the ALB and targets, so Option D is not required for this specific goal. Option A is incorrect because Client Certificate Authentication is for mutual TLS between client and ALB. Option C is incorrect because adding a listener rule based on path affects traffic routing, not encryption. Option E is incorrect because security group rules control access but do not encrypt traffic.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Enable Client Certificate Authentication on the ALB
Why it's wrong here
This is for client authentication, not encrypting traffic to targets.
- ✓
Configure the target group to use HTTPS as the protocol
Why this is correct
HTTPS target group ensures traffic from ALB to targets is encrypted.
- ✗
Add a listener rule to forward traffic based on path
Why it's wrong here
Listener rules are for routing, not encryption.
- ✗
Configure the ALB listener to use HTTPS
Why it's wrong here
HTTPS listener terminates SSL and can re-encrypt to targets.
- ✗
Configure security groups to allow only HTTPS traffic
Why it's wrong here
Security groups allow or deny traffic but do not encrypt it.
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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 needs to encrypt data in transit between an Application Load Balancer and EC2 instances. Which TWO actions should they take?
easy- A.Create a TCP listener on the ALB.
- B.Place Amazon CloudFront in front of the ALB.
- ✓ C.Upload a certificate to AWS Certificate Manager (ACM).
- ✓ D.Configure the ALB target group to use HTTPS protocol.
- E.Use a self-signed certificate on the EC2 instances.
Why C: To encrypt traffic between the ALB and EC2 instances, you need to upload a certificate to AWS Certificate Manager (ACM) for the backend HTTPS listener (Option C) and configure the ALB target group to use HTTPS protocol (Option D). Option A (TCP listener) does not support encryption. Option B (CloudFront) is a CDN and not required for backend encryption. Option E (self-signed certificate) is not recommended for production environments.
Variation 2. A company wants to encrypt data in transit between an Application Load Balancer (ALB) and its backend targets. Which AWS service should be used to terminate TLS at the ALB and re-encrypt traffic to the targets?
easy- A.AWS Certificate Manager (ACM)
- B.AWS Shield
- ✓ C.Application Load Balancer with HTTPS listeners
- D.AWS WAF
Why C: An ALB can terminate TLS and optionally re-encrypt traffic to targets using HTTPS. Option A is wrong because AWS Certificate Manager provides certificates, not encryption. Option B is wrong because AWS Shield is for DDoS protection. Option C is correct. Option D is wrong because AWS WAF is a web application firewall.
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.