Quick Answer
The answer is that the bandwidth limit of the virtual interface is being exceeded. When traffic on a single 1 Gbps VIF surpasses its capacity during peak hours, packets are queued and eventually dropped, forcing TCP retransmissions that directly cause the observed latency spike. This tests your understanding of how Direct Connect bandwidth limits interact with TCP congestion control, a core concept for the AWS Certified Advanced Networking Specialty ANS-C01 exam. A common trap is to blame BGP timers or jumbo frames, but remember that BGP affects routing convergence, not throughput latency, and jumbo frames actually reduce overhead. The key insight is that a bandwidth limit exceeded scenario manifests as increased latency, not total disconnection, which distinguishes it from VLAN mismatches. Memory tip: think of a single-lane highway at rush hour—when the bandwidth limit is exceeded, traffic slows down due to congestion, not because the road is broken.
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 troubleshooting high latency on an AWS Direct Connect connection. The network team notices that the latency increases during peak hours. The connection uses a single virtual interface (VIF) with a 1 Gbps capacity. What is the MOST likely cause of the latency?
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.
The VLAN ID is mismatched between the customer router and AWS
Why wrong: VLAN mismatch would cause loss of connectivity.
The bandwidth limit of the virtual interface is being exceeded
Congestion causes packet drops and increased latency.
Jumbo frames are not enabled on the customer router
Why wrong: Jumbo frames reduce overhead and latency.
BGP keepalive timers are set too high
Why wrong: BGP timers affect session stability, not latency.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
The bandwidth limit of the virtual interface is being exceeded
Option B is correct because traffic can be dropped if it exceeds the bandwidth limit, causing retransmissions and increased latency. Option A is wrong because jumbo frames typically reduce latency. Option C is wrong because BGP timers affect convergence, not latency. Option D is wrong because VLAN mismatch would cause connectivity loss, not just latency.
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
For each option: why learners choose it and why it is or isn't the right answer here.
The VLAN ID is mismatched between the customer router and AWS
Why it's wrong here
VLAN mismatch would cause loss of connectivity.
The bandwidth limit of the virtual interface is being exceeded
Why this is correct
Congestion causes packet drops and increased latency.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Access ports place end devices into a single VLAN.
Jumbo frames are not enabled on the customer router
Why it's wrong here
Jumbo frames reduce overhead and latency.
BGP keepalive timers are set too high
Why it's wrong here
BGP timers affect session stability, not latency.
Common exam traps
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
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.
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
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
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.
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FAQ
Network Implementation — This question tests Network Implementation — Access ports place end devices into a single VLAN..
The correct answer is: The bandwidth limit of the virtual interface is being exceeded — Option B is correct because traffic can be dropped if it exceeds the bandwidth limit, causing retransmissions and increased latency. Option A is wrong because jumbo frames typically reduce latency. Option C is wrong because BGP timers affect convergence, not latency. Option D is wrong because VLAN mismatch would cause connectivity loss, not just latency.
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.
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Access ports place end devices into a single VLAN.
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Last reviewed: Jun 20, 2026
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