The answer is to enable the Elastic Network Adapter (ENA) and enhanced networking on both EC2 instances, as this is the single most impactful step for achieving ultra-low latency. Enhanced networking with ENA bypasses the traditional virtualization overhead by providing direct access to the underlying hardware, significantly reducing packet processing latency and jitter for TCP traffic. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this question tests your understanding that while a cluster placement group co-locates instances to minimize network distance, it does not automatically enable the high-performance driver needed to exploit that proximity; a common trap is assuming the placement group alone is sufficient. Remember the memory tip: “Placement groups get you close, but ENA gets you fast.”
ANS-C01 Network Implementation Practice Question
This ANS-C01 practice question tests your understanding of network implementation. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 implementing a network architecture for a critical application that requires ultra-low latency between two Amazon EC2 instances. The instances are launched in two different Availability Zones within the same AWS Region. The network engineer needs to ensure that traffic between the instances uses the lowest latency path possible. The instances are placed in a cluster placement group. The application uses TCP. The engineer has configured the security groups to allow all traffic between the instances. However, latency is higher than expected. What should the engineer do to reduce latency?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Enable Elastic Network Adapter (ENA) and enhanced networking on both instances.
Option A is correct because Elastic Network Adapter (ENA) with enhanced networking provides lower latency and higher throughput. Option B is incorrect because cluster placement group is already used. Option C is incorrect because using private IP ensures traffic stays within AWS network, but ENA is more impactful. Option D is incorrect because VPC peering does not help; instances are in same VPC.
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.
✗
Configure the instances to use their private IP addresses instead of public IPs for communication.
Why it's wrong here
Private IP is default; not the issue.
✓
Enable Elastic Network Adapter (ENA) and enhanced networking on both instances.
Why this is correct
ENA reduces latency by offloading network processing.
Move the instances to the same subnet within the same Availability Zone.
Why it's wrong here
Already in cluster placement group; same AZ would help but not as much as ENA.
✗
Set up a VPC peering connection between the subnets in the two Availability Zones.
Why it's wrong here
Instances are in same VPC; peering unnecessary.
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
An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.
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 Implementation — This question tests Network Implementation — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Enable Elastic Network Adapter (ENA) and enhanced networking on both instances. — Option A is correct because Elastic Network Adapter (ENA) with enhanced networking provides lower latency and higher throughput. Option B is incorrect because cluster placement group is already used. Option C is incorrect because using private IP ensures traffic stays within AWS network, but ENA is more impactful. Option D is incorrect because VPC peering does not help; instances are in same VPC.
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.
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Question Discussion
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