ANS-C01 Network Design Practice Test 32 — 15 Questions

Question 1

A company has a VPC with a CIDR block of 10.0.0.0/16. They need to add a new CIDR block 10.1.0.0/16 to accommodate more subnets. The VPC already has multiple subnets and route tables. What is the impact of adding this secondary CIDR?

Choose an answer to begin — your selection is scored in the full session.

Accepted Answer

Existing subnets and route tables remain unchanged; new subnets can be created in the new CIDR.. Adding a secondary CIDR block to an existing VPC is a non-disruptive operation. The existing subnets and route tables remain completely unchanged because the secondary CIDR is an additional IP address space, not a modification of the existing one. New subnets can be created within the new CIDR block, and you must explicitly associate them with route tables as needed.

Answer

The secondary CIDR will be automatically advertised to all route tables.

Answer

The VPC will experience a brief outage while the new CIDR is being associated.

Answer

Existing subnets will automatically be extended to include IPs from the new CIDR.

Question 2

A company is designing a VPC for a three-tier application (web, application, database). The database tier should not be accessible from the internet, but the web tier must be accessible. Which subnet design should the network engineer use?

Accepted Answer

Place web servers in public subnets with an internet gateway, and app and database servers in private subnets.. It places the web servers in a public subnet with an Internet Gateway (IGW) to allow inbound HTTP/HTTPS traffic from the internet, while the application and database servers are placed in private subnets with no direct internet path. This design ensures the database tier is isolated from the internet, meeting the security requirement, while the web tier remains accessible. The application servers can communicate with the database via private IP addresses within the VPC, and outbound internet access for the private subnets (if needed) can be provided through a NAT Gateway in a public subnet.

Answer

Place web and app servers in public subnets, and database servers in private subnets.

Answer

Place all servers in private subnets and use a NAT Gateway for internet access.

Answer

Place all servers in public subnets and rely on security group rules to restrict access.

Question 3

A company has a VPC with CIDR 10.0.0.0/16 and two subnets: 10.0.1.0/24 (public) and 10.0.2.0/24 (private). The company wants to add a new subnet for a third tier. Which of the following are valid subnet CIDRs that can be added? (Select TWO.)

Accepted Answer

10.0.3.0/24. (10.0.3.0/24) is correct because it falls within the VPC CIDR 10.0.0.0/16 and does not overlap with the existing subnets (10.0.1.0/24 and 10.0.2.0/24). The /24 prefix length matches the existing subnet structure, and the third octet (3) is outside the range of the first two subnets, ensuring no IP address conflict.

Answer

10.0.1.128/25

Answer

10.1.0.0/16

Answer

10.0.2.64/26

Question 4

A company is designing a Direct Connect solution for high availability. Which of the following are best practices? (Select THREE.)

Accepted Answer

Provision two Direct Connect connections at different locations.. Provisioning two Direct Connect connections at different locations ensures physical diversity, which is a fundamental requirement for high availability. If one data center or fiber path fails, the other connection can continue to carry traffic, preventing a single point of failure. This aligns with the AWS Well-Architected Framework's recommendation for redundant network paths.

Answer

Use the same Direct Connect provider for both connections to simplify management.

Answer

Use a single Direct Connect connection with multiple virtual interfaces.

Question 5

A company is designing a VPC with IPv6. Which components are required to enable IPv6 communication between instances in the VPC and the internet? (Select TWO.)

Accepted Answer

A route in the subnet route table to ::/0 to the internet gateway. To enable IPv6 communication between instances in a VPC and the internet, you need an internet gateway (IGW) attached to the VPC, and a route in the subnet's route table that directs IPv6 traffic (destination ::/0) to that internet gateway. The IGW performs NAT for IPv6 (using eUI-64 addresses) and allows bidirectional traffic, so both components are required.

Answer

An egress-only internet gateway

Answer

A VPC peering connection to a VPC with internet access

Answer

A NAT Gateway

Question 6

A company has a VPC with CIDR 172.16.0.0/16. They have two subnets: 172.16.1.0/24 (public) and 172.16.2.0/24 (private) in us-west-2a. They have an EC2 instance in the private subnet that needs to access an S3 bucket for log uploads. The company wants to avoid using a NAT Gateway to reduce costs. The S3 bucket is in the same region. Which solution should the network engineer implement?

Accepted Answer

Create a VPC Gateway Endpoint for S3 and add a route from the private subnet to the endpoint.. A VPC Gateway Endpoint for S3 allows private subnet resources to access S3 without traversing the internet or requiring a NAT Gateway. The endpoint uses AWS PrivateLink to route traffic directly to S3 over the AWS network, and you must add a route in the private subnet's route table pointing to the endpoint (prefix list ID) to enable connectivity.

Answer

Assign an IAM instance profile to the EC2 instance that allows S3 access.

Answer

Set up a VPN connection from the VPC to the S3 bucket.

Answer

Create an S3 access point and configure the VPC to use it.

Question 7

A company has a VPC with public and private subnets in two Availability Zones. The private subnets host EC2 instances that need to access the internet for software updates. The company must ensure that traffic from the private instances uses a single, predictable public IP address. What is the MOST cost-effective solution?

Accepted Answer

Deploy a NAT Gateway in a public subnet in one Availability Zone, and route private subnet traffic to it.. A NAT Gateway in a public subnet provides outbound-only internet access for private instances, and it uses a single Elastic IP address, ensuring a predictable public IP. This is the most cost-effective managed solution, as NAT Gateways are highly available within an Availability Zone and require no manual instance management.

Answer

Attach an Internet Gateway to the VPC and update the private subnet route table with a default route to the Internet Gateway.

Answer

Create a Transit Gateway with a VPC attachment and route traffic through a central egress VPC.

Answer

Launch a NAT instance in a public subnet and configure source/destination check.

Question 8

A company is using AWS Direct Connect to connect its on-premises data center to AWS. The company has a single hosted virtual interface (VIF) with a private VIF to a VPC. The network team notices that traffic from on-premises to AWS is asymmetric—some packets go through the Direct Connect while others use a VPN backup. The team wants all traffic to use Direct Connect when available. What should they do?

Accepted Answer

Advertise more specific prefixes (e.g., /24) over Direct Connect and less specific (e.g., /16) over VPN.. BGP route selection prefers more specific prefixes (longest prefix match) over less specific ones. By advertising a more specific prefix (e.g., /24) over Direct Connect and a less specific prefix (e.g., /16) over the VPN, the on-premises router will prefer the Direct Connect path for the more specific route, ensuring all traffic uses Direct Connect when available. This leverages BGP's prefix-length-based path selection without requiring removal of the VPN backup.

Answer

Disable AS_PATH prepending on the Direct Connect BGP session.

Answer

Convert the private VIF to a public VIF.

Answer

Remove the VPN connection to force all traffic through Direct Connect.

Question 9

A company is using AWS Transit Gateway to connect multiple VPCs and on-premises networks. The network team notices that traffic between two VPCs is taking a suboptimal path through the on-premises network instead of staying within AWS. What is the MOST likely cause?

Accepted Answer

The Transit Gateway route tables do not have a route for the destination VPC CIDR, so traffic is sent to the on-premises network via a default route.. When a Transit Gateway route table lacks a specific route for the destination VPC CIDR, traffic destined for that VPC is evaluated against the remaining routes. If a default route (0.0.0.0/0) exists pointing to an on-premises network attachment (e.g., a VPN or Direct Connect), the traffic will be forwarded over that path, resulting in a suboptimal route that leaves AWS and re-enters through the on-premises network. This is the most likely cause because the Transit Gateway performs destination-based routing, and missing a specific VPC route forces fallback to the default route.

Answer

The subnet route tables in each VPC have a route pointing to the other VPC's CIDR via the Internet Gateway.

Answer

The VPCs are peered directly, bypassing the Transit Gateway.

Answer

Security groups are blocking traffic between the VPCs.

Question 10

A company has a VPC with a public subnet and a private subnet. An EC2 instance in the private subnet needs to download patches from the internet. The instance is behind a NAT Gateway in the public subnet. The download is failing. Which configuration should the network engineer check FIRST?

Accepted Answer

The route table associated with the private subnet has a default route (0.0.0.0/0) pointing to the NAT Gateway.. For an EC2 instance in a private subnet to reach the internet via a NAT Gateway, the private subnet's route table must have a default route (0.0.0.0/0) pointing to the NAT Gateway. Without this route, traffic from the instance destined for the internet has no path to the NAT Gateway, causing the download to fail.

Answer

The network ACL for the private subnet allows inbound HTTP/HTTPS traffic.

Answer

The EC2 instance has a public IP address assigned.

Answer

The Internet Gateway is attached to the private subnet.

Question 11

A company is deploying a new application in a VPC that uses a single Availability Zone. The application consists of an Application Load Balancer (ALB) in a public subnet and EC2 instances in a private subnet. The EC2 instances need to send logs to an Amazon S3 bucket. The company has created a VPC gateway endpoint for S3 and associated it with the route table for the private subnet. The EC2 instances have an instance profile that grants access to the S3 bucket. However, the log delivery fails. The network team has verified that the route table for the private subnet includes a route to the S3 prefix list via the gateway endpoint. What is the MOST likely cause of the failure?

Accepted Answer

The VPC endpoint policy does not allow the PutObject action on the S3 bucket.. The most likely cause is that the VPC endpoint policy does not allow the PutObject action on the S3 bucket. Even though the route table has a route to the S3 prefix list via the gateway endpoint and the EC2 instance profile grants access, the endpoint policy acts as an additional layer of authorization. If the endpoint policy does not explicitly allow the s3:PutObject action for the target bucket, requests will be denied, causing the log delivery to fail.

Answer

The route table does not have a route to the S3 prefix list.

Answer

The VPC endpoint is not configured with private DNS.

Answer

The security group on the EC2 instances does not allow outbound traffic to the S3 prefix list.

Question 12

An organization has multiple VPCs connected to a common Transit Gateway. The network team wants to centrally manage and enforce routing policies, such as allowing or denying traffic between specific VPCs based on tags. Which AWS feature should be used to implement this requirement?

Accepted Answer

AWS Transit Gateway Network Manager. AWS Transit Gateway Network Manager provides a central dashboard to manage and monitor transit gateways, on-premises networks, and attached VPCs. It supports defining and enforcing routing policies based on tags, enabling the network team to centrally allow or deny traffic between specific VPCs without manually managing individual route tables.

Answer

AWS Direct Connect Gateway

Answer

Amazon Route 53 Resolver

Answer

VPC Peering with route tables

Question 13

A network engineer is troubleshooting connectivity to a VPC endpoint service. The engineer runs the CLI command shown in the exhibit. The output shows two service names. Which statement is correct based on this output?

Accepted Answer

The engineer can create an interface VPC endpoint to the services. The CLI command `aws ec2 describe-vpc-endpoint-services` returns a list of AWS services that support VPC endpoints. The output shows two service names, which are AWS-managed services (e.g., `com.amazonaws.vpce.us-east-1.s3`). These services can be accessed via interface VPC endpoints, which use Elastic Network Interfaces (ENIs) with private IP addresses to route traffic privately within the VPC. Therefore, the engineer can create an interface VPC endpoint to these services.

Answer

The services are Gateway VPC endpoints

Answer

The services are VPC peering connections

Answer

The services are Gateway Load Balancer endpoint services

Question 14

A company is designing a disaster recovery solution that requires replicating data from an on-premises database to an Amazon RDS instance in a different AWS region. The data transfer must be encrypted in transit and should not traverse the public internet. Which approach meets these requirements?

Accepted Answer

Establish an AWS Site-to-Site VPN over an AWS Direct Connect connection. An AWS Site-to-Site VPN over an AWS Direct Connect connection provides encrypted IPsec tunnels for data in transit while keeping traffic entirely within the private network, avoiding the public internet. The Direct Connect private VIF establishes a dedicated private link to AWS, and the VPN overlay adds encryption, meeting both requirements for an on-premises to RDS cross-region replication scenario.

Answer

Use an AWS Direct Connect connection with public VIF

Answer

Establish an AWS Site-to-Site VPN over the internet

Answer

Use VPC Peering between the on-premises network and the RDS VPC

Question 15

A company has multiple VPCs in the same AWS region that need to communicate with each other. The network team wants to minimize the number of connections and simplify management. The solution must support transitive routing between all VPCs. Which AWS service should be used?

Accepted Answer

AWS Transit Gateway. AWS Transit Gateway (TGW) is a network transit hub that enables transitive routing between multiple VPCs and on-premises networks through a single gateway. It uses a hub-and-spoke architecture, which inherently supports transitive routing (e.g., VPC A can reach VPC C via the TGW without requiring direct peering between A and C). This minimizes the number of connections (N VPCs require only N attachments instead of N*(N-1)/2 VPC peering connections) and simplifies management with a central routing table.

Answer

VPC Peering

Answer

AWS Direct Connect Gateway

Answer

VPC Endpoints