This ANS-C01 practice question tests your understanding of network design. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 VIF to a VPC. They want to add a second Direct Connect connection for redundancy. Both connections will terminate at the same Direct Connect gateway. Which TWO steps are required to enable BGP multipath (ECMP) across the two connections?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Ensure the same customer-side ASN is used on both virtual interfaces.
To enable BGP multipath (ECMP) across two Direct Connect connections terminating on the same Direct Connect gateway, you must use the same customer-side ASN on both virtual interfaces. This allows the Direct Connect gateway to treat both paths as equal-cost routes. Additionally, you must advertise the same BGP prefixes on both virtual interfaces so that the gateway sees identical routes from both paths and can load-balance traffic across them.
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.
✓
Ensure the same customer-side ASN is used on both virtual interfaces.
Why this is correct
Same ASN is required for ECMP.
Related concept
Read the scenario before looking for a memorised answer.
✗
Use a different autonomous system number (ASN) on each virtual interface.
Why it's wrong here
Different ASNs would break ECMP.
✗
Advertise different BGP prefixes on each virtual interface.
Why it's wrong here
Different prefixes would not be equal cost.
✓
Advertise the same BGP prefixes (routes) on both virtual interfaces.
Why this is correct
Same prefixes are needed for ECMP.
Related concept
Read the scenario before looking for a memorised answer.
✗
Attach each virtual interface to a different VPC.
Why it's wrong here
ECMP requires same VPC target.
Common exam traps
Common exam trap: answer the scenario, not the keyword
AWS often tests the misconception that using different ASNs or different prefixes is required for redundancy, but the key to ECMP is identical ASN and identical prefixes to enable equal-cost multipath routing.
Detailed technical explanation
How to think about this question
BGP multipath (ECMP) relies on the BGP best-path selection algorithm; when the same ASN and same prefixes are received from multiple peers, the router considers them as equal-cost paths and installs them in the routing table for load balancing. In AWS Direct Connect, the Direct Connect gateway acts as the BGP speaker, and it requires identical AS_PATH length (achieved by same customer ASN) and identical NLRI (same prefixes) to enable ECMP. A real-world scenario is a dual-homed on-premises network where both connections must be active-active; failing to match ASNs would result in one path being preferred over the other.
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 startup's cloud architect reviews their monthly bill and notices costs are higher than expected for a long-running batch job. Switching from on-demand instances to Reserved Instances — or using Spot/Preemptible VMs — can reduce compute costs by up to 72 %. Questions like this test whether you understand the tradeoffs between commitment, flexibility, and cost across cloud pricing models.
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: Ensure the same customer-side ASN is used on both virtual interfaces. — To enable BGP multipath (ECMP) across two Direct Connect connections terminating on the same Direct Connect gateway, you must use the same customer-side ASN on both virtual interfaces. This allows the Direct Connect gateway to treat both paths as equal-cost routes. Additionally, you must advertise the same BGP prefixes on both virtual interfaces so that the gateway sees identical routes from both paths and can load-balance traffic across them.
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.
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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