ANS-C01 Network Design Practice Test 3 — 15 Questions

Question 1

A network engineer is setting up a cross-account Route 53 Resolver rule association. The engineer creates the above resource-based policy on a resolver rule in account 111111111111. The engineer then tries to associate the rule from account 222222222222 but receives an access denied error. What is the MOST likely reason for the failure?

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

Accepted Answer

The policy's Principal is set to account 111111111111 instead of account 222222222222.. The resource-based policy on the Route 53 Resolver rule must specify the consuming account (222222222222) as the Principal to authorize cross-account association. Since the policy incorrectly sets the Principal to the owning account (111111111111), the request from account 222222222222 lacks the required permissions, resulting in an access denied error.

Answer

The policy does not allow the 'route53resolver:AssociateResolverRule' action.

Answer

The policy does not include the 'route53resolver:DisassociateResolverRule' action.

Answer

The resolver rule is not shared with account 222222222222.

Question 2

A company has a VPC with public and private subnets in two Availability Zones. An Application Load Balancer in the public subnets distributes traffic to EC2 instances in the private subnets. The security group for the EC2 instances allows inbound traffic from the ALB security group. Users report intermittent timeouts. What is the most likely cause?

Accepted Answer

The network ACL for the private subnets is blocking inbound traffic from the ALB subnets.. Intermittent timeouts are often caused by network ACL rules that block ephemeral ports used for return traffic. The ALB initiates connections to EC2 instances on random ephemeral ports (1024-65535). If the private subnet's network ACL denies inbound traffic on these ports from the ALB subnets, connections will fail intermittently. In contrast, a missing inbound rule on the ALB security group would result in consistent failures, not intermittent ones.

Answer

The security group for the ALB does not allow inbound traffic from the internet.

Answer

The ALB is not associated with an internet gateway.

Answer

Cross-zone load balancing is disabled on the ALB.

Question 3

A solutions architect is designing a VPC with public and private subnets in two Availability Zones. The private subnets require outbound internet access for software updates, but inbound internet access must be blocked. Which solution meets these requirements?

Accepted Answer

Deploy a NAT Gateway in a public subnet and add a default route to the NAT Gateway in the private subnet route tables.. A NAT Gateway, deployed in a public subnet with an Elastic IP and a route to an Internet Gateway, enables outbound traffic from private subnets to the internet while blocking unsolicited inbound connections. The private subnet route table directs default traffic (0.0.0.0/0) to the NAT Gateway, which performs source network address translation (SNAT) on outbound packets, ensuring responses return to the NAT Gateway without exposing private instances directly.

Answer

Attach an internet gateway to the VPC and add a default route to the internet gateway in the private subnet route tables.

Answer

Launch an EC2 instance in a public subnet with a proxy software and route private subnet traffic through it.

Answer

Create a VPC endpoint for Amazon S3 and add a route to the endpoint in the private subnet route tables.

Question 4

A company has a Direct Connect connection with a private VIF to a VPC. The VPC has a virtual private gateway attached. The on-premises network advertises a specific route 10.0.0.0/16, but the VPC uses the same CIDR 10.0.0.0/16. The company requires connectivity to the VPC from on-premises but cannot change the VPC CIDR. What is the most cost-effective solution?

Accepted Answer

Create a Transit Gateway with a VPN attachment to on-premises and use route table separation.. A Transit Gateway with a VPN attachment allows you to use route table separation to isolate the overlapping CIDR (10.0.0.0/16) between the on-premises network and the VPC. By creating separate route tables for the VPN attachment and the VPC attachment, you can control traffic flow and avoid routing conflicts without changing the VPC CIDR. This is the most cost-effective solution as it leverages existing VPN connectivity and avoids the expense of migrating workloads or provisioning additional infrastructure.

Answer

Use VPC peering between the on-premises network and the VPC.

Answer

Set up a Direct Connect Gateway and attach the VPC and on-premises networks.

Answer

Create a new VPC with a different CIDR and migrate workloads.

Question 5

A company's VPC has an internet gateway and a NAT Gateway in a public subnet. The private subnet route table has a default route pointing to the NAT Gateway. EC2 instances in the private subnet can access the internet, but cannot access an on-premises network connected via AWS Site-to-Site VPN. What is the most likely cause?

Accepted Answer

The private subnet route table does not have a route to the on-premises network via the virtual private gateway.. The private subnet route table has a default route (0.0.0.0/0) pointing to the NAT Gateway, which allows outbound internet traffic. However, traffic destined for the on-premises network must be routed via the Virtual Private Gateway (VGW) attached to the VPC. Since the route table lacks a specific route (e.g., 10.0.0.0/8) pointing to the VGW, packets to the on-premises CIDR are instead sent to the NAT Gateway, which drops them because it has no route or interface for the on-premises network.

Answer

The NAT Gateway is not configured to route traffic to the VPN.

Answer

The internet gateway is not attached to the VPC.

Answer

The VPN connection is not advertising the on-premises CIDR via BGP.

Question 6

A company is designing a multi-VPC architecture in the same region. The VPCs need to communicate with each other using private IP addresses. The company must minimize cost and operational overhead. Which solution should the company use?

Accepted Answer

Create VPC peering connections between each pair of VPCs.. VPC peering connections provide direct, private IP connectivity between VPCs using the AWS global network, with no bandwidth bottlenecks or single points of failure. It is the most cost-effective solution for a small number of VPCs (e.g., fewer than 10) as there are no hourly charges for the peering connection itself—only data transfer costs. This minimizes operational overhead compared to managing VPN tunnels or a Transit Gateway, as peering is a simple, one-to-one relationship that does not require additional appliances or complex routing policies.

Answer

Set up AWS Site-to-Site VPN connections between each VPC.

Answer

Use ClassicLink to connect the VPCs.

Answer

Create a Transit Gateway and attach all VPCs.

Question 7

A company has a VPC with an internet gateway and a NAT Gateway. The private subnet route table has a default route to the NAT Gateway. The company wants to enable instances in the private subnet to access an S3 bucket in the same region without traversing the internet. Which TWO actions should the company take?

Accepted Answer

Add a route to the S3 prefix list via the gateway endpoint in the private subnet route table.. Adding a route to the S3 prefix list via the gateway endpoint directs traffic destined for S3 through the VPC endpoint, keeping it within the AWS network. Option C is correct because a gateway VPC endpoint for S3 provides a private, scalable connection to S3 without requiring internet access or a NAT Gateway. Together, these actions allow private subnet instances to access S3 privately and efficiently.

Answer

Remove the default route to the NAT Gateway from the private subnet route table.

Answer

Add a route to the S3 prefix list via the NAT Gateway in the private subnet route table.

Answer

Create an interface VPC endpoint for S3.

Question 8

A company has a Direct Connect connection with a private VIF attached to a virtual private gateway. The VPC has multiple subnets in two Availability Zones. The on-premises network advertises a default route (0.0.0.0/0) via BGP. The company wants all internet-bound traffic from the VPC to go through the on-premises network. Which THREE actions are required to achieve this?

Accepted Answer

Add a default route pointing to the virtual private gateway in the private subnet route tables.. Adding a default route (0.0.0.0/0) pointing to the virtual private gateway in the private subnet route tables ensures that all internet-bound traffic from those subnets is forwarded over the Direct Connect private VIF to the on-premises network. This leverages the BGP-advertised default route from the on-premises network, allowing the company to enforce its security and routing policies for internet access.

Answer

Deploy a NAT Gateway in a public subnet.

Answer

Attach an internet gateway to the VPC.

Question 9

A company runs a multi-tier web application on AWS. The web servers in public subnets need to send traffic to the application servers in private subnets. The application servers must only accept traffic from the web servers. Both tiers are in the same VPC. Which design meets these requirements without introducing a single point of failure or unnecessary complexity?

Accepted Answer

Place the web servers in a public subnet with a security group that allows inbound from 0.0.0.0/0 on port 443. Place the app servers in a private subnet with a security group that allows inbound from the web server security group on the application port.. It uses security group referencing, which allows the app servers' security group to dynamically allow traffic from any instance associated with the web servers' security group, regardless of IP address changes. This design avoids a single point of failure by not introducing any load balancer or gateway, and it minimizes complexity by leveraging native VPC security group behavior within the same VPC.

Answer

Place the web servers and app servers in the same private subnet behind an internal Network Load Balancer. Route web traffic through the NLB.

Answer

Place the web servers in a public subnet with an Internet Gateway. Place the app servers in a private subnet with a NAT Gateway for outbound traffic. Use NACLs to allow inbound from the web subnet CIDR.

Answer

Place the web servers in a public subnet with a NACL allowing inbound on port 443. Place the app servers in a private subnet with a NACL allowing inbound from the web subnet CIDR on the application port.

Question 10

A network engineer is designing a hybrid network architecture that connects an on-premises data center to AWS using AWS Direct Connect. The company requires high availability and wants to minimize operational overhead. The on-premises network uses BGP to advertise routes to AWS. Which design meets these requirements?

Accepted Answer

Provision two Direct Connect connections to two different Direct Connect locations, each with a private VIF to the same VPC. Use BGP over the VIFs.. Provisioning two Direct Connect connections to two different Direct Connect locations ensures physical and path diversity, eliminating single points of failure. Using BGP over the private VIFs allows dynamic route advertisement and automatic failover, meeting high availability requirements while minimizing operational overhead through managed BGP sessions.

Answer

Provision one Direct Connect connection with a private VIF and a site-to-site VPN connection as a backup.

Answer

Provision one Direct Connect connection with two virtual interfaces (VIFs) to the same AWS device.

Answer

Provision two Direct Connect connections to the same Direct Connect location, both with private VIFs to the same VPC.

Question 11

A company is designing a VPC with public and private subnets for a three-tier web application. The web tier must be accessible from the internet, the application tier must only be accessible from the web tier, and the database tier must only be accessible from the application tier. Which combination of route tables and security groups achieves this?

Accepted Answer

Public subnet route table: 0.0.0.0/0 -> Internet Gateway. Web SG: allow 0.0.0.0/0 on port 443. App SG: allow from Web SG. DB SG: allow from App SG.. It uses an Internet Gateway (IGW) in the public subnet route table to enable inbound internet traffic to the web tier, and security groups (SGs) are referenced by logical ID (Web SG, App SG, DB SG) to enforce strict, stateful traffic flow: Web SG allows HTTPS from 0.0.0.0/0, App SG allows traffic only from Web SG, and DB SG allows traffic only from App SG. This layered SG approach ensures that each tier can only be reached from the preceding tier, meeting the access requirements without relying on network ACLs or routing.

Answer

Public subnet route table: 0.0.0.0/0 -> NAT Gateway. Web SG: allow 0.0.0.0/0 on port 443. App SG: allow from Web SG. DB SG: allow from App SG.

Answer

Private subnet route table: 0.0.0.0/0 -> Internet Gateway. Web SG: allow 0.0.0.0/0 on port 443. App SG: allow from Web SG. DB SG: allow from App SG.

Answer

Public subnet route table: 0.0.0.0/0 -> Internet Gateway. Web SG: allow 0.0.0.0/0 on port 443. App SG: allow from Web SG. DB SG: allow from 0.0.0.0/0 on port 3306.

Question 12

A company is deploying an application that requires low-latency communication between EC2 instances in two different AWS Regions. The application traffic is latency-sensitive and the company wants to minimize jitter. Which network design provides the lowest and most consistent latency?

Accepted Answer

Deploy an AWS Global Accelerator with endpoints in both Regions and use the accelerator's static IP addresses for communication.. AWS Global Accelerator uses the AWS global network and Anycast static IP addresses to route traffic over optimized paths, providing lower and more consistent latency than VPC peering, internet transit, or VPNs. It minimizes jitter by avoiding the public internet and leveraging AWS's internal backbone, which is ideal for latency-sensitive inter-Region communication.

Answer

Create a VPC peering connection between the two VPCs and route traffic through the peering connection.

Answer

Use internet gateways and route traffic over the public internet between the instances.

Answer

Use a Site-to-Site VPN connection between the two VPCs over the internet.

Question 13

A company has a VPC with a CIDR of 10.0.0.0/16. They need to connect to two on-premises data centers, each with overlapping CIDR blocks (192.168.0.0/16). The company wants to use AWS Site-to-Site VPN with dynamic routing (BGP). Which design allows the VPC to reach both data centers without route conflicts?

Accepted Answer

Create two separate virtual private gateways, each in a different VPC, and use VPC peering. Alternatively, use a transit gateway with separate VPN attachments and BGP communities to tag routes.. Overlapping CIDR blocks cannot be advertised to the same virtual private gateway (VPG) without causing route conflicts. By using a transit gateway with separate VPN attachments, each data center's routes are isolated in separate route tables, and BGP communities can be used to tag and differentiate routes. This design allows the VPC to reach both data centers by leveraging the transit gateway's ability to manage overlapping prefixes through separate route tables and path selection.

Answer

Create two VPN connections to a single virtual private gateway and advertise the same CIDR from both data centers. Use BGP AS_PATH prepending to influence routing.

Answer

Create a single VPN connection with two tunnels to the same virtual private gateway. Use different BGP ASNs for each data center.

Answer

Create two VPN connections to the same virtual private gateway. Use static routes with different metric values.

Question 14

Which TWO of the following are valid components of an AWS Transit Gateway design for connecting multiple VPCs and on-premises networks?

Accepted Answer

Transit Gateway route table. A Transit Gateway route table is a fundamental component that controls how traffic is routed between attachments (VPCs, VPNs, Direct Connect) within the Transit Gateway. Each attachment is associated with exactly one route table, and route propagation enables dynamic learning of routes across the network.

Answer

VPC Endpoint Gateway

Answer

Transit Gateway endpoint attached to a subnet in a VPC

Answer

Direct Connect Gateway associated with a Transit Gateway

Question 15

Which THREE of the following are valid considerations when designing a multi-Region active-active application using AWS Global Accelerator?

Accepted Answer

You can assign different weights to endpoints in different Regions to control traffic distribution.. AWS Global Accelerator allows you to assign different weights to endpoints in different Regions, enabling granular control over traffic distribution for active-active architectures. This is achieved through endpoint group weights, where you can adjust the proportion of traffic sent to each Regional endpoint group, supporting scenarios like gradual rollouts or load balancing across Regions.

Answer

Global Accelerator supports sticky sessions (session affinity) based on client IP.

Answer

Global Accelerator provides a set of static IP addresses that are unique to each Region.