The answer is enabling jumbo frames on the transit VPC's EC2-based virtual appliances. This resolves the issue because intermittent connectivity in a hub-and-spoke VPN topology often stems from an MTU mismatch across the long-haul path, where packets traversing from ap-southeast-1 to eu-west-1 via the us-east-1 transit VPC become fragmented or dropped. By increasing the maximum transmission unit on the transit appliances, you reduce fragmentation and allow larger packets to pass cleanly, stabilizing the connection. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this scenario tests your understanding of how MTU and fragmentation affect VPN performance in multi-region hub-and-spoke designs, a common trap where candidates focus on VPN status rather than path-level packet handling. Remember: if the VPN is up but connectivity is spotty, think MTU—jumbo frames on transit appliances often fix the hop-by-hop fragmentation.
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.
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 AWS Site-to-Site VPN connection to its respective on-premises office. Users report intermittent connectivity issues when accessing a web application hosted in a spoke VPC in eu-west-1 from an on-premises office in ap-southeast-1. The network engineer checks the VPN connection and finds it is up. Which design change would MOST likely resolve the issue?
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
✓
Enable jumbo frames on the transit VPC's EC2-based virtual appliances.
The issue is intermittent connectivity between an on-premises office in ap-southeast-1 and a spoke VPC in eu-west-1, traversing a transit VPC in us-east-1. The VPN is up, so the problem is likely packet fragmentation or MTU mismatch across the long-haul path. Enabling jumbo frames on the transit VPC's EC2-based virtual appliances (e.g., firewall or router instances) increases the maximum transmission unit, reducing fragmentation and improving performance for large packets, which is a common cause of intermittent issues in hub-and-spoke topologies.
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.
✗
Change the VPN connection from static to dynamic routing.
Why it's wrong here
Routing type does not affect latency.
✓
Enable jumbo frames on the transit VPC's EC2-based virtual appliances.
Why this is correct
Jumbo frames reduce overhead and improve throughput for large packets.
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.
✗
Enable BGP route propagation on the transit VPC's route tables.
Why it's wrong here
Route propagation is likely already enabled.
✗
Deploy a new transit VPC in eu-west-1.
Why it's wrong here
Adding another transit VPC increases complexity.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume a 'VPN is up' means the issue is routing-related (e.g., BGP propagation or static vs. dynamic), but the real culprit is often subtle packet-level problems like MTU mismatch or fragmentation across a multi-region hub-and-spoke design.
Detailed technical explanation
How to think about this question
EC2-based virtual appliances in a transit VPC often use software like Cisco Cloud Services Router (CSR) or AWS Marketplace firewalls, which have default MTU settings (e.g., 1500 bytes). When traffic traverses multiple VPN tunnels and regions, the IPsec encapsulation adds overhead (up to ~60 bytes), causing packets to exceed the path MTU and trigger fragmentation or drops. Enabling jumbo frames (e.g., MTU 9001) on these appliances allows larger payloads, reducing the chance of fragmentation and improving throughput for applications like web hosting.
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 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.
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: Enable jumbo frames on the transit VPC's EC2-based virtual appliances. — The issue is intermittent connectivity between an on-premises office in ap-southeast-1 and a spoke VPC in eu-west-1, traversing a transit VPC in us-east-1. The VPN is up, so the problem is likely packet fragmentation or MTU mismatch across the long-haul path. Enabling jumbo frames on the transit VPC's EC2-based virtual appliances (e.g., firewall or router instances) increases the maximum transmission unit, reducing fragmentation and improving performance for large packets, which is a common cause of intermittent issues in hub-and-spoke topologies.
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.
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Question Discussion
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