The correct action is to configure the LGW VLAN interface with the VLAN ID that matches the on-premises VLAN. This is because AWS Outposts Layer 2 extension relies on the local gateway (LGW) to bridge the on-premises broadcast domain into the Outposts VPC; if the VLAN IDs do not match, the LGW cannot forward Ethernet frames between the on-premises switch and the Outposts subnet, breaking Layer 2 adjacency. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this scenario tests your understanding that Outposts Layer 2 extension is not a routed solution—it requires the LGW VLAN interface to be configured with the exact same VLAN ID as the existing on-premises network to preserve the broadcast domain and allow legacy applications to communicate without IP changes. A common trap is assuming a Layer 3 service like VPC peering or Transit Gateway can solve this, but those operate at Layer 3 and cannot extend a VLAN. Memory tip: think of the LGW VLAN interface as a virtual patch cable—both ends must be on the same VLAN ID to complete the circuit.
ANS-C01 Network Implementation Practice Question
This ANS-C01 practice question tests your understanding of network implementation. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A company is migrating its on-premises data center to AWS and wants to extend its Layer 2 network to AWS using AWS Outposts. The company has an existing VLAN with IP subnet 10.0.1.0/24 that hosts a legacy application requiring direct Layer 2 connectivity between on-premises servers and Outposts racks. The network engineer has installed an Outposts rack in the data center and connected it to the on-premises network via a local gateway (LGW) with a VLAN interface. The engineer has created a subnet in the Outposts VPC with CIDR 10.0.1.0/24 and launched EC2 instances. However, the on-premises servers cannot communicate with the Outposts instances. The LGW is configured correctly. Which action should the engineer take to resolve the issue?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Configure the LGW VLAN interface with the correct VLAN ID that matches the on-premises VLAN.
Option C is correct because the LGW VLAN interface must be associated with the same VLAN ID as the on-premises network to allow Layer 2 communication. Option A is incorrect because a VPC peering connection is Layer 3, not Layer 2. Option B is incorrect because Direct Connect is not needed. Option D is incorrect because a Transit Gateway does not provide Layer 2 extension.
Key principle: A trunk being up does not mean the VLAN is allowed across it. Always verify the allowed VLAN list and whether the VLAN exists on both switches.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
Configure the LGW VLAN interface with the correct VLAN ID that matches the on-premises VLAN.
Common exam trap: an active trunk can still block the VLAN you need
A trunk being up does not prove every VLAN is crossing it. Check allowed VLAN lists, native VLAN mismatch, VLAN existence and access-port assignment.
Detailed technical explanation
How to think about this question
VLAN questions usually combine access-port and trunking clues. The key is to identify whether the issue is local to one switchport, caused by the trunk, or caused by the VLAN not existing where it needs to exist.
KKey Concepts to Remember
Access ports place end devices into a single VLAN.
Trunk ports carry multiple VLANs between switches.
Allowed VLAN lists decide which VLANs can cross a trunk.
Native VLAN mismatch can create confusing symptoms.
TExam Day Tips
→Use show vlan brief to verify access VLANs.
→Use show interfaces trunk to verify trunk state and allowed VLANs.
→Do not treat every same-VLAN issue as a routing problem.
Key takeaway
A trunk being up does not mean the VLAN is allowed across it. Always verify the allowed VLAN list and whether the VLAN exists on both switches.
Real-world example
How this comes up in practice
A company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
What to study next
Got this wrong? Here's your next step.
Review VLAN allowed lists, native VLAN mismatch detection, and how to verify VLAN membership with show vlan brief and show interfaces trunk. Then practise related ANS-C01 questions on switching, trunking, and access-port configuration.
Network Implementation — This question tests Network Implementation — Access ports place end devices into a single VLAN..
What is the correct answer to this question?
The correct answer is: Configure the LGW VLAN interface with the correct VLAN ID that matches the on-premises VLAN. — Option C is correct because the LGW VLAN interface must be associated with the same VLAN ID as the on-premises network to allow Layer 2 communication. Option A is incorrect because a VPC peering connection is Layer 3, not Layer 2. Option B is incorrect because Direct Connect is not needed. Option D is incorrect because a Transit Gateway does not provide Layer 2 extension.
What should I do if I get this ANS-C01 question wrong?
Review VLAN allowed lists, native VLAN mismatch detection, and how to verify VLAN membership with show vlan brief and show interfaces trunk. Then practise related ANS-C01 questions on switching, trunking, and access-port configuration.
What is the key concept behind this question?
Access ports place end devices into a single VLAN.
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Question Discussion
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