The answer is one route in each VPC’s route table. This is correct because VPC Peering requires only a single explicit route in each VPC pointing to the peering connection for the destination CIDR of the other VPC—so VPC A needs a route for 10.1.0.0/16 via the peering ID, and VPC B needs a route for 10.0.0.0/16 via the same peering ID. No route is needed for a VPC’s own CIDR, as local routes are implicit, and only one peering connection exists between the two VPCs. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this concept tests your understanding of the minimal routing required for bidirectional communication, often appearing as a straightforward question that traps candidates into overcomplicating with unnecessary entries. A common memory tip is “one hop, one route per peer CIDR”—each VPC only needs a route to the other’s network, not to itself or to multiple connections.
ANS-C01 Network Design Practice Question
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 VPC with a CIDR of 10.0.0.0/16. They want to connect this VPC to a second VPC with CIDR 10.1.0.0/16 using VPC Peering. The VPCs are in the same account and Region. What is the minimum number of route table entries needed in each VPC to enable full bidirectional communication?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "minimum / minimize"
Why it matters: Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
One route in each VPC's route table
Option A is correct because each VPC needs one route pointing to the peering connection for the other VPC's CIDR. Option B is wrong because each VPC does not need a route for its own CIDR. Option C is wrong because there is only one peering connection. Option D is wrong because explicit routes are required.
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.
✗
Two routes in each VPC's route table: one for the local CIDR and one for the peer CIDR
Why it's wrong here
Local CIDR routes are automatically added; only peer CIDR needs explicit route.
✗
No routes are needed because VPC Peering automatically enables communication
Why it's wrong here
Explicit routes must be added to route tables.
✓
One route in each VPC's route table
Why this is correct
Each VPC needs a route to the peer VPC's CIDR via the peering connection.
Clue confirmation
The clue word "minimum / minimize" in the question point toward this answer.
Both VPCs need routes to the peer CIDR for bidirectional communication.
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.
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 Design — This question tests Network Design — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: One route in each VPC's route table — Option A is correct because each VPC needs one route pointing to the peering connection for the other VPC's CIDR. Option B is wrong because each VPC does not need a route for its own CIDR. Option C is wrong because there is only one peering connection. Option D is wrong because explicit routes are required.
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.
Are there clue words in this question I should notice?
Yes — watch for: "minimum / minimize". Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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