- A
Verify that the Direct Connect virtual interface is in the 'available' state.
Why wrong: Incorrect. While the virtual interface must be available for connectivity, the stem implies the connection exists but routing is the issue. The VIF state could be 'available' even if BGP is not established.
- B
Verify that the VPC route table has a route to the on-premises CIDR pointing to the virtual private gateway.
Why wrong: Incorrect. The stem states that the VPC route table already has the route to the on-premises CIDR via the VGW. Verifying this route would not resolve the issue as it is already configured.
- C
Verify that the BGP session between the on-premises router and the VGW is established.
Correct. A BGP session between the on-premises router and the VGW is required for route exchange. If the session is down, the on-premises router will not have a route to the VPC CIDR, preventing reachability.
- D
Verify that the on-premises router is advertising the VPC CIDR.
Why wrong: Incorrect. The on-premises router should be receiving the VPC CIDR route from the VGW via BGP. The issue is likely that the VGW is not advertising the VPC CIDR due to a BGP problem, or the on-premises router is not receiving it. Verification should focus on BGP session status first.
Direct Connect Connectivity: Missing VPC Route to On-Premises CIDR
This ANS-C01 practice question tests your understanding of network management and operations. 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 has a Direct Connect connection with a private virtual interface. The on-premises network team reports that they cannot reach EC2 instances in a VPC. The VPC has a virtual private gateway attached. The route table in the VPC has a route to the on-premises CIDR via the virtual private gateway. What should the network engineer verify?
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
Verify that the BGP session between the on-premises router and the VGW is established.
Option C is correct because even though the VPC route table has the route to the on-premises CIDR via the virtual private gateway, the on-premises router cannot reach EC2 instances if the BGP session between the on-premises router and the VGW is not established. Without a functioning BGP session, the VGW cannot exchange routes with the on-premises router, causing connectivity failure. Options A and B are not the primary issue: A checks the virtual interface state, but the VIF could be available yet BGP down; B is already stated as present. Option D is incorrect because the on-premises router needs to receive the VPC CIDR route from the VGW via BGP, not advertise it back.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Verify that the Direct Connect virtual interface is in the 'available' state.
Why it's wrong here
Incorrect. While the virtual interface must be available for connectivity, the stem implies the connection exists but routing is the issue. The VIF state could be 'available' even if BGP is not established.
- ✗
Verify that the VPC route table has a route to the on-premises CIDR pointing to the virtual private gateway.
Why it's wrong here
Incorrect. The stem states that the VPC route table already has the route to the on-premises CIDR via the VGW. Verifying this route would not resolve the issue as it is already configured.
- ✓
Verify that the BGP session between the on-premises router and the VGW is established.
- ✗
Verify that the on-premises router is advertising the VPC CIDR.
Why it's wrong here
Incorrect. The on-premises router should be receiving the VPC CIDR route from the VGW via BGP. The issue is likely that the VGW is not advertising the VPC CIDR due to a BGP problem, or the on-premises router is not receiving it. Verification should focus on BGP session status first.
Common exam traps
Common exam trap: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Detailed technical explanation
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
- CIDR notation defines the prefix length.
- Block size helps identify subnet boundaries.
- Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
- The required host count determines the smallest suitable subnet.
TExam Day Tips
- Write the block size before choosing the subnet.
- Check whether the question asks for hosts, subnets or a specific address range.
- Do not confuse /24, /25, /26 and /27 host counts.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
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.
Visual reference
What to study next
Got this wrong? Here's your next step.
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related ANS-C01 subnetting questions on CIDR, address ranges, and subnet selection.
- →
Network Management and Operations — study guide chapter
Learn the concepts, then practise the questions
- →
Network Management and Operations practice questions
Targeted practice on this topic area only
- →
All ANS-C01 questions
1,705 questions across all exam domains
- →
AWS Certified Advanced Networking Specialty ANS-C01 study guide
Full concept coverage aligned to exam objectives
- →
ANS-C01 practice test guide
How to use practice tests most effectively before exam day
Related practice questions
Related ANS-C01 practice-question pages
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
Network Management and Operations practice questions
Practise ANS-C01 questions linked to Network Management and Operations.
Network Security, Compliance and Governance practice questions
Practise ANS-C01 questions linked to Network Security, Compliance and Governance.
Network Design practice questions
Practise ANS-C01 questions linked to Network Design.
Network Implementation practice questions
Practise ANS-C01 questions linked to Network Implementation.
ANS-C01 fundamentals practice questions
Practise ANS-C01 questions linked to ANS-C01 fundamentals.
ANS-C01 scenario practice questions
Practise ANS-C01 questions linked to ANS-C01 scenario.
ANS-C01 troubleshooting practice questions
Practise ANS-C01 questions linked to ANS-C01 troubleshooting.
Practice this exam
Start a free ANS-C01 practice session
Short sessions build daily habit. Longer sessions build exam-day stamina. Try a timed session to simulate real conditions.
FAQ
Questions learners often ask
What does this ANS-C01 question test?
Network Management and Operations — This question tests Network Management and Operations — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Verify that the BGP session between the on-premises router and the VGW is established. — Option C is correct because even though the VPC route table has the route to the on-premises CIDR via the virtual private gateway, the on-premises router cannot reach EC2 instances if the BGP session between the on-premises router and the VGW is not established. Without a functioning BGP session, the VGW cannot exchange routes with the on-premises router, causing connectivity failure. Options A and B are not the primary issue: A checks the virtual interface state, but the VIF could be available yet BGP down; B is already stated as present. Option D is incorrect because the on-premises router needs to receive the VPC CIDR route from the VGW via BGP, not advertise it back.
What should I do if I get this ANS-C01 question wrong?
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related ANS-C01 subnetting questions on CIDR, address ranges, and subnet selection.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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 →
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 has a Direct Connect connection with multiple virtual interfaces (VIFs). They notice that traffic from on-premises to a VPC is being dropped. The VPC is associated with a private VIF. The on-premises router has a BGP route to the VPC's CIDR. The VPC's route table has a route to the virtual private gateway. What is the MOST likely cause of the dropped traffic?
hard- ✓ A.The VPC route table does not have a route pointing to the virtual private gateway for the on-premises CIDR
- B.The MTU size on the Direct Connect connection is too small
- C.The BGP session is not established
- D.The allowed prefixes on the virtual private gateway do not include the on-premises CIDR
Why A: Option A is correct because for traffic to flow from on-premises to the VPC, the VPC must have a route back to the on-premises CIDR pointing to the virtual private gateway. Without that route, the return traffic will be dropped. Option B is incorrect because MTU issues typically cause packet fragmentation or loss, not complete drop due to missing routes. Option C is incorrect because the BGP session is established (as indicated by the BGP route being present). Option D is incorrect because allowed prefixes on the virtual private gateway control which routes can be advertised over BGP, not the return path in the VPC route table.
Variation 2. A company has set up a Direct Connect connection with a private VIF to its VPC. The BGP session is up, but traffic is not passing between the on-premises network and the VPC. Which configuration should be verified?
medium- A.Ensure jumbo frames are enabled on the Direct Connect interface
- B.Verify that the VIF is a public VIF
- C.Review the Direct Connect virtual interface metrics in CloudWatch
- ✓ D.Check the BGP advertised routes and the VPC route tables
Why D: Option D is correct because for traffic to flow between on-premises and the VPC over a Direct Connect private VIF, the on-premises network must advertise the appropriate routes via BGP, and the VPC route tables must have routes pointing to the virtual private gateway (VGW). Option A is wrong because jumbo frames are not required for basic connectivity. Option B is wrong because the VIF type (private vs public) is not the issue—the BGP session is already up, indicating the VIF is correctly configured as private. Option C is wrong because CloudWatch metrics are for monitoring performance, not for diagnosing routing issues.
Keep practising
More ANS-C01 practice questions
- A financial services company has a VPC with a public subnet and a private subnet. EC2 instances in the private subnet ne…
- A company is designing a network security architecture for a multi-account environment using AWS Transit Gateway. The se…
- A company is using AWS Direct Connect to connect its on-premises network to AWS. The company wants to encrypt all traffi…
- A company uses AWS Transit Gateway to connect multiple VPCs and on-premises networks via AWS Site-to-Site VPN. The secur…
- A company runs a web application on EC2 instances behind an Application Load Balancer (ALB). The application must be acc…
- A global e-commerce company uses a hub-and-spoke network topology with a transit VPC in us-east-1. Each spoke VPC has an…
Last reviewed: Jun 20, 2026
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.