ANS-C01 Network Implementation Practice Question
Network Topology
Refer to the exhibit. A Lambda function is attached to a VPC using the network interface eni-1234567890abcdef0. The Lambda function needs to send traffic to an on-premises server via a Direct Connect connection. The traffic is failing. Which setting on the network interface is most likely causing the issue?
⚠ Common exam trap
The ANS-C01 exam often tests the Source/Destination Check flag as a hidden default setting that candidates forget to disable when an ENI is used for forwarding traffic, leading them to incorrectly blame routing or security groups.
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
✓
The SourceDestCheck flag is enabled, which prevents the Lambda function from sending traffic that it is not the source or destination of.
Lambda functions attached to a VPC use elastic network interfaces (ENIs) with the Source/Destination Check flag enabled by default. This flag causes the ENI to drop any traffic where the ENI's IP address is not the source or destination of the packet. Since the Lambda function is sending traffic to an on-premises server via Direct Connect, the ENI is acting as an intermediate hop, and the flag must be disabled for the traffic to pass.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The network interface is in a subnet that does not have a route to the Direct Connect.
Why it's wrong here
The route table is not shown, but the exhibit does not indicate a routing issue.
- ✗
The network interface has two private IP addresses.
Why it's wrong here
Multiple IP addresses are allowed and do not cause traffic failure.
- ✓
The SourceDestCheck flag is enabled, which prevents the Lambda function from sending traffic that it is not the source or destination of.
Why this is correct
Lambda functions that forward traffic need to disable source/destination check.
- ✗
The security group attached to the network interface may be blocking outbound traffic.
Why it's wrong here
Possible but not indicated; the SourceDestCheck is a more direct cause for forwarding scenarios.
Quick reference
Cloud Service Model Comparison
| Model | You Manage | Provider Manages | Examples |
|---|---|---|---|
| IaaS | OS, runtime, apps, data | Hardware, hypervisor, networking | EC2, Azure VMs, GCP Compute Engine |
| PaaS | Apps and data | OS, runtime, middleware, hardware | Elastic Beanstalk, Azure App Service |
| SaaS | Data and settings only | Everything else | Microsoft 365, Salesforce, Workday |
| FaaS / Serverless | Function code only | Infra, scaling, runtime | Lambda, Azure Functions, Cloud Run |
| CaaS | Containers and apps | Kubernetes, OS, hardware | EKS, AKS, GKE |
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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.