ANS-C01 Network Implementation Practice Question
Network Topology
A network engineer runs the above command and sees an ENI (eni-0a1b2c3d4e5f6g7h8) with status 'in-use' but no InstanceId attached. What AWS service is most likely using this ENI?
⚠ Common exam trap
The ANS-C01 exam often tests the misconception that an ENI in 'in-use' status must always be attached to an EC2 instance, leading candidates to overlook managed services like RDS that use ENIs without exposing the InstanceId.
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
✓
An Amazon RDS database instance.
An Amazon RDS database instance uses an Elastic Network Interface (ENI) as its primary network interface, and when the RDS instance is in a 'stopped' or 'failed' state, the ENI may remain in 'in-use' status without an InstanceId attached. This is because RDS manages its own ENI independently of EC2 instances, and the ENI persists even when the database instance is not running.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
A VPC endpoint (Interface type).
Why it's wrong here
Interface endpoint ENIs have descriptions like 'VPC Endpoint'.
- ✓
An Amazon RDS database instance.
Why this is correct
RDS uses managed ENIs with 'RDS-managed' description.
- ✗
A NAT gateway.
Why it's wrong here
NAT gateway ENIs have descriptions like 'NAT Gateway'.
- ✗
An AWS Transit Gateway.
Why it's wrong here
Transit Gateway does not use ENIs; it uses attachments.
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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.