The answer is that the VPC route table lacks a route to the on-premises network pointing to the Virtual Private Gateway (VGW). Even when a Direct Connect private VIF is in the 'available' state—confirming that Layer 2 connectivity and BGP sessions are up—traffic cannot flow into the VPC without a specific route in the VPC route table that directs the on-premises CIDR block to the VGW. This is a classic gotcha on the AWS Certified Advanced Networking Specialty ANS-C01 exam, testing your understanding that a healthy VIF and BGP session are necessary but not sufficient for end-to-end traffic flow; the VPC itself must have a routing path. Many engineers mistakenly focus only on the Direct Connect side or BGP advertisements, forgetting that the VPC route table is the final gatekeeper. Remember the mnemonic: VIF up, BGP up, but no route? No flow. Always check the VPC route table first when troubleshooting Direct Connect private VIF traffic not flowing.
ANS-C01 Network Design Practice Question
This ANS-C01 practice question tests your understanding of network design. 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.
Network Topology
A network engineer is troubleshooting a Direct Connect private VIF. The VIF is in 'available' state but traffic is not flowing to the VPC. The VGW is attached to the VPC. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The VPC route table lacks a route to the on-premises network pointing to the VGW.
When a Direct Connect private VIF is in the 'available' state, the physical and logical layer 2 connectivity is established, and BGP sessions are typically up. However, traffic still cannot flow to the VPC unless the VPC route table contains a route that directs traffic destined for the on-premises network to the Virtual Private Gateway (VGW). Without this route, the VPC has no path to send traffic over the Direct Connect connection, even though the VIF and BGP are operational.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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 VPC route table lacks a route to the on-premises network pointing to the VGW.
Why this is correct
Without this route, traffic cannot be forwarded.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The route filter prefix for the VPC CIDR is misconfigured.
Why it's wrong here
It shows 10.0.0.0/16, which is correct.
✗
BGP is not established between the on-premises router and the VGW.
Why it's wrong here
BGP is used for route exchange, but the VIF state indicates routing is configured.
✗
The VIF state is not 'available'.
Why it's wrong here
It is 'available'.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume an 'available' VIF and established BGP automatically mean traffic flows, but they overlook the critical requirement of a VPC route table entry pointing to the VGW as the next hop.
Trap categories for this question
Command / output trap
It shows 10.0.0.0/16, which is correct.
Detailed technical explanation
How to think about this question
In AWS Direct Connect, a private VIF requires a route in the VPC route table pointing to the VGW for traffic to be forwarded to the on-premises network. Even with BGP sessions established and routes propagated via the VGW, the VPC's routing table must explicitly contain a destination route (e.g., 10.0.0.0/8) with the VGW as the target. This is a common misconfiguration because engineers often assume that BGP route propagation alone is sufficient, but the VPC route table acts as the final arbiter for traffic forwarding.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A healthcare organisation deploys an application with a public-facing web tier and a private database tier. The database subnet has no public IP and only accepts connections from the web tier's security group. Questions like this test whether you can design cloud network isolation using VNets/VPCs, subnets, and security group rules.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Network Design — This question tests Network Design — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The VPC route table lacks a route to the on-premises network pointing to the VGW. — When a Direct Connect private VIF is in the 'available' state, the physical and logical layer 2 connectivity is established, and BGP sessions are typically up. However, traffic still cannot flow to the VPC unless the VPC route table contains a route that directs traffic destined for the on-premises network to the Virtual Private Gateway (VGW). Without this route, the VPC has no path to send traffic over the Direct Connect connection, even though the VIF and BGP are operational.
What should I do if I get this ANS-C01 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
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.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.