ANS-C01 Practice Exam 3 — 20 Questions

Question 1

A company is migrating a legacy on-premises application to AWS. The application uses a large number of short-lived TCP connections and requires low latency. The network team is considering using either a Network Load Balancer (NLB) or a Gateway Load Balancer (GWLB). Which of the following is a key advantage of using NLB over GWLB for this use case?

Accepted Answer

NLB preserves the client source IP, while GWLB does not by default.. For an application using a large number of short-lived TCP connections requiring low latency, NLB is the optimal choice because it operates at Layer 4 and preserves the client source IP address by default, which is critical for applications that need to log or process the original client IP. GWLB, by design, uses GENEVE encapsulation (UDP port 6081) to tunnel traffic to backend appliances, which replaces the client source IP with the NLB's private IP unless explicit configuration (e.g., proxy protocol) is used. This makes NLB the better fit for preserving source IP without additional overhead.

Answer

NLB can forward traffic to third-party virtual appliances.

Answer

NLB can handle higher throughput than GWLB.

Answer

NLB supports TLS termination, while GWLB does not.

Question 2

A company is deploying a hybrid network architecture with an AWS Site-to-Site VPN connection between its on-premises network and a VPC. The on-premises network uses BGP to advertise routes to the VPN connection. After the VPN is established, the on-premises network cannot reach EC2 instances in the VPC. The VPC route table has a route for the on-premises CIDR block pointing to the VPN gateway. What is the most likely cause of this issue?

Accepted Answer

The on-premises network is advertising a default route (0.0.0.0/0) via BGP, which is overriding the VPC's local route.. When the on-premises network advertises a default route (0.0.0.0/0) via BGP over the VPN connection, the VPC propagates that route into its route tables (if route propagation is enabled). This default route can override the VPC's local route for the on-premises CIDR, causing traffic destined for the on-premises network to be sent back out the VPN gateway instead of being delivered locally, effectively breaking connectivity to EC2 instances.

Answer

The VPN connection is not using the correct pre-shared key.

Answer

The security group attached to the EC2 instances does not allow inbound traffic from the on-premises CIDR.

Answer

The VPC's network ACLs are blocking inbound traffic from the on-premises network.

Question 3

A company is designing a network for a three-tier web application in a single VPC. The web tier must be accessible from the internet, but the application and database tiers must not have direct internet access. The application servers need to make outbound calls to a third-party API. Which architecture meets these requirements?

Accepted Answer

Web servers in public subnets with an Application Load Balancer, application servers in private subnets with a NAT gateway, and database servers in private subnets.. Option C is correct because it places web servers in public subnets with an Application Load Balancer for inbound internet traffic, while application and database servers reside in private subnets without direct internet access. A NAT gateway in a public subnet enables the application servers to initiate outbound connections to a third-party API, with return traffic automatically routed back, meeting the requirement for outbound-only internet access.

Answer

Web servers in public subnets, application and database servers in private subnets with an internet gateway for outbound traffic.

Answer

All servers in public subnets with security groups restricting access.

Answer

All servers in private subnets and a VPN connection to the internet.

Question 4

A company is using AWS Direct Connect with a private VIF to access their VPC. Users report intermittent connectivity issues. You check the Direct Connect console and see that the virtual interface state is 'down'. What is the MOST likely cause?

Accepted Answer

BGP session between the customer router and AWS is down.. A private VIF relies on a BGP session between the customer router and the AWS Direct Connect router to exchange routes and maintain the virtual interface state. When the BGP session goes down, the VIF state transitions to 'down' because no routing information is being exchanged, causing connectivity loss. This is the most direct and common cause of a VIF being in the 'down' state.

Answer

AWS Site-to-Site VPN is not established.

Answer

MACsec encryption is misconfigured on the customer router.

Answer

Jumbo frames are enabled on the VIF but not supported by the customer router.

Question 5

A network engineer is troubleshooting high latency on an AWS Transit Gateway that connects multiple VPCs and an on-premises network via AWS Site-to-Site VPN. The engineer wants to identify potential causes. Which TWO actions should the engineer take? (Choose two.)

Accepted Answer

Review the CloudWatch metrics for the VPN tunnels for packet loss and latency.. Option B is correct because CloudWatch metrics for VPN tunnels provide direct visibility into packet loss and latency, which are key indicators of performance issues on the AWS Site-to-Site VPN component of the Transit Gateway. Option C is correct because Transit Gateway Flow Logs capture IP traffic information between attachments, allowing the engineer to analyze traffic patterns, identify drops, and pinpoint which VPC or VPN attachment is contributing to the high latency.

Answer

Review the NACL rules for each subnet in the VPCs.

Answer

Re-create the VPN connections to reset the tunnels.

Answer

Enable VPC Flow Logs on the VPCs attached to the transit gateway.

Question 6

A company has a VPC with public and private subnets. The security team wants to inspect all traffic between the private subnets and the internet using a centralized inspection VPC. The company uses AWS Network Firewall and wants to ensure that traffic cannot bypass the firewall. Which TWO actions should the company take? (Choose TWO.)

Accepted Answer

Deploy the Network Firewall in a dedicated inspection VPC and use a VPC peering or transit gateway to route traffic from the workload VPC to the inspection VPC.. Option B is correct because deploying AWS Network Firewall in a dedicated inspection VPC and using a transit gateway (or VPC peering) allows centralized traffic inspection. This architecture ensures that all traffic between the workload VPC and the internet is routed through the inspection VPC, preventing bypass. The transit gateway enables transitive routing, while VPC peering can also be used with proper route table entries to force traffic through the firewall.

Answer

Configure an AWS WAF web ACL and associate it with the internet gateway.

Answer

Enable VPC Flow Logs on the private subnets to monitor traffic.

Answer

Create an internet gateway in the workload VPC and attach it to the private subnets.

Question 7

A company is designing a hybrid network using AWS Transit Gateway. The company has three VPCs (VPC-A, VPC-B, VPC-C) all attached to the same Transit Gateway. The on-premises network connects to the Transit Gateway via a Direct Connect gateway. The company needs to ensure that VPC-C can communicate with the on-premises network but not with VPC-A or VPC-B. Which TWO actions should the network engineer take?

Accepted Answer

Associate the VPC-C route table with the Direct Connect gateway attachment.. Option B is correct because associating the VPC-C route table with the Direct Connect gateway attachment allows VPC-C to exchange routes with the on-premises network via the Transit Gateway, enabling communication. Option D is correct because creating a separate Transit Gateway route table for VPC-C and not propagating VPC-A and VPC-B routes ensures that VPC-C has no routes to those VPCs, effectively isolating it from them at the network layer.

Answer

Use security groups on VPC-C to deny traffic from VPC-A and VPC-B.

Answer

Establish VPC peering connections between VPC-C and VPC-A, and VPC-C and VPC-B.

Answer

Apply a network ACL on VPC-C subnets to block traffic from VPC-A and VPC-B.

Question 8

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.. Option B is correct because 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 9

A company is designing a multi-region architecture with VPCs in us-east-1 and eu-west-1. The company needs low-latency connectivity between the VPCs and wants to avoid traffic over the public internet. The VPCs have overlapping CIDR blocks (10.0.0.0/16). Which solution should the network engineer recommend?

Accepted Answer

Set up an AWS Transit Gateway in each region and connect them via a VPN attachment.. Option A is correct because AWS Transit Gateway supports inter-region peering attachments that use the AWS global network backbone, providing low-latency, private connectivity between VPCs in different regions. Even when VPCs have overlapping CIDR blocks, Transit Gateway can handle this through route table isolation and network segmentation (e.g., using separate route tables for each VPC attachment), which VPC peering cannot do. VPN attachments between Transit Gateways in each region establish encrypted tunnels over the AWS backbone, avoiding the public internet.

Answer

Use a Direct Connect connection between the regions.

Answer

Use VPC peering between the two VPCs.

Answer

Place all resources in a single VPC with multiple Availability Zones.

Question 10

A company has a Direct Connect connection with two private virtual interfaces (VIFs) to two different VPCs in the same AWS Region. The company wants to use AWS Transit Gateway to simplify connectivity between these VPCs and their on-premises network. Which steps are required to integrate the existing Direct Connect connection with Transit Gateway?

Accepted Answer

Create a Direct Connect gateway, associate the existing VIFs, and attach the Direct Connect gateway to the Transit Gateway.. Option D is correct because AWS Direct Connect private VIFs cannot be attached directly to a Transit Gateway. Instead, you must create a Direct Connect Gateway, associate the existing private VIFs with it, and then attach the Direct Connect Gateway to the Transit Gateway. This architecture allows the Transit Gateway to route traffic between the on-premises network (via the Direct Connect connection) and the attached VPCs, while also enabling inter-VPC routing through the Transit Gateway.

Answer

Set up a VPN connection over the Direct Connect link and attach the VPN to the Transit Gateway.

Answer

Attach the existing private VIFs directly to the Transit Gateway.

Answer

Create a new private VIF on the Direct Connect connection and attach it to the Transit Gateway.

Question 11

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.. Option A is correct because 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 12

A company is designing a multi-Region architecture using AWS Transit Gateway and Direct Connect. They have VPCs in us-east-1 and eu-west-1, each with an attached Transit Gateway. The Direct Connect gateway is associated with the Transit Gateway in us-east-1. They need to enable communication between VPCs across Regions using the Direct Connect gateway. What is the correct design to achieve this?

Accepted Answer

Create a Transit Gateway peering attachment between the Transit Gateways in us-east-1 and eu-west-1, and route traffic over the Direct Connect gateway via the peering.. Option C is correct because Transit Gateway peering attachments allow transitive routing between Transit Gateways in different AWS Regions. By establishing a peering attachment between the Transit Gateways in us-east-1 and eu-west-1, traffic from the VPC in eu-west-1 can be routed through its local Transit Gateway, across the peering attachment to the Transit Gateway in us-east-1, and then over the Direct Connect gateway to on-premises networks. This design enables cross-region VPC communication via Direct Connect without requiring a single Transit Gateway or direct VPC peering.

Answer

Create a single Transit Gateway that spans both Regions and attach VPCs in both Regions.

Answer

Use VPC peering between the VPCs and route Direct Connect traffic through the VPC peering connection.

Answer

Associate the Direct Connect gateway with both Transit Gateways in us-east-1 and eu-west-1.

Question 13

A company is deploying a multi-tier web application across two AWS Regions. The application uses an Application Load Balancer (ALB) in each region, and traffic must be distributed to the closest healthy ALB using Route 53 latency-based routing. The application requires that clients maintain the same source IP address when the request is forwarded from the ALB to the backend targets. The backend targets are EC2 instances in private subnets. The company also needs to ensure that traffic between the ALB and targets stays within AWS. What should the company implement to meet these requirements?

Accepted Answer

Deploy an internal ALB in each region. Place targets in private subnets. Use VPC endpoints for the ALB (AWS PrivateLink) and Route 53 latency-based routing to the VPC endpoint.. Option B is correct because an internal ALB with targets in private subnets ensures traffic stays within AWS and preserves the client source IP by using VPC endpoints (AWS PrivateLink). Route 53 latency-based routing directs traffic to the closest healthy VPC endpoint, meeting the multi-region distribution requirement while maintaining source IP transparency for backend targets.

Answer

Deploy a Network Load Balancer (NLB) in each region with targets in public subnets. Use Route 53 latency-based routing to the NLB.

Answer

Deploy an Application Load Balancer (ALB) with internet-facing scheme in each region. Use Route 53 latency-based routing to the ALB.

Answer

Use AWS Global Accelerator with endpoints in each region. Attach the ALB as an endpoint and enable client IP preservation on the accelerator.

Answer

Deploy an ALB with internet-facing scheme in each region. Use Route 53 latency-based routing to the ALB. Place targets in public subnets to preserve source IP.

Question 14

A network engineer is designing a hybrid network architecture that connects an on-premises data center to AWS using AWS Direct Connect and a VPN connection as a backup. The on-premises network uses BGP to advertise routes to AWS. Which of the following are best practices for this setup? (Choose TWO.)

Accepted Answer

Use different BGP ASNs for the Direct Connect and VPN connections.. Option B is correct because using different BGP ASNs for the Direct Connect and VPN connections prevents BGP from treating the two connections as a single eBGP session, which would cause routing loops or suboptimal path selection. This separation allows AWS to distinguish between the two paths and apply independent routing policies. Option E is correct because configuring BGP attributes (such as AS path prepending or MED) on the Direct Connect path ensures it is preferred over the VPN backup, aligning with the design goal of using Direct Connect as the primary link.

Answer

Advertise the same routes over both connections with identical BGP attributes.

Answer

Use the VPN connection as the primary path and Direct Connect as the backup.

Answer

Use the same BGP ASN for both the Direct Connect and VPN connections.

Question 15

A company is implementing a hybrid network with AWS Direct Connect and a VPN connection as backup. They have a Direct Connect gateway (DXGW) attached to a private VIF and a virtual private gateway (VGW) attached to a VPN connection. The VPC is attached to the VGW. They want to use the Direct Connect connection for all traffic when available. The on-premises router advertises the same prefix over both connections. However, traffic from on-premises to the VPC is using the VPN connection. BGP is configured correctly on both connections. What should the company do to prefer the Direct Connect path?

Accepted Answer

Configure a lower MED (Multi-Exit Discriminator) on the Direct Connect VIF.. Option E is correct because the Multi-Exit Discriminator (MED) is a BGP attribute used to influence inbound traffic from an AS to the local AS. By setting a lower MED on the Direct Connect VIF, the on-premises router will prefer the Direct Connect path over the VPN path when both advertise the same prefix, assuming all other BGP path selection criteria are equal. This directly addresses the requirement to prefer the Direct Connect connection for all traffic.

Answer

Set a higher weight on the Direct Connect BGP session.

Answer

Set a higher local preference on the Direct Connect VIF.

Answer

Change the BGP timers on the Direct Connect VIF to have a lower hold time.

Answer

Configure AS_PATH prepending on the VPN BGP session.

Question 16

A company is setting up a Direct Connect connection to connect its on-premises data center to AWS. The connection is established, and a private virtual interface (VIF) is configured. The on-premises router can ping the VIF's Amazon side IP address, but cannot ping an EC2 instance in the VPC. The VPC has a virtual private gateway attached, and the route tables are correctly configured. What should the company check next?

Accepted Answer

Verify that the on-premises router is advertising the VPC CIDR to the Direct Connect router.. The on-premises router can ping the VIF's Amazon side IP, confirming that Layer 2 and Layer 3 connectivity over the Direct Connect link is working, and BGP is established. However, the inability to ping the EC2 instance indicates that return traffic from the VPC is not reaching the on-premises network. For return traffic to be routed correctly, the on-premises router must advertise the VPC CIDR (or a specific prefix) to the Direct Connect router via BGP; otherwise, the AWS side will not forward traffic destined for the on-premises network over the VIF.

Answer

Check that the NACLs on the EC2 instance's subnet allow inbound ICMP.

Answer

Confirm that the private VIF is associated with the correct virtual private gateway.

Answer

Ensure that BGP is established and receiving routes.

Question 17

A company has a VPC with multiple subnets spanning three Availability Zones. They have deployed an Application Load Balancer (ALB) in the VPC and need to ensure high availability and scalability for a web application. Which of the following are design considerations for implementing the ALB in this environment? (Choose THREE.)

Accepted Answer

Enable the ALB in at least two Availability Zones to provide high availability.. Option A is correct because AWS requires an Application Load Balancer to be enabled in at least two Availability Zones to achieve high availability. If one AZ fails, the ALB can continue routing traffic to healthy targets in the remaining AZs, ensuring fault tolerance and compliance with the ALB's regional service model.

Answer

Configure the ALB to use subnets that span multiple Availability Zones.

Answer

Use VPC peering to connect the ALB to subnets in other VPCs.

Question 18

A company uses AWS Client VPN to provide remote access to its VPC resources. Users report that they can connect to the VPN but cannot reach any resources in the VPC. The VPN endpoint is associated with a subnet in VPC A. The VPC's route table has a route for the Client VPN CIDR (10.200.0.0/16) pointing to the VPN endpoint. The security group assigned to the VPN endpoint allows inbound traffic from the VPN clients. What is the most likely cause of the issue?

Accepted Answer

The security group associated with the VPN endpoint does not allow inbound traffic from the VPN client CIDR.. The most likely cause is that the security group associated with the VPN endpoint does not allow inbound traffic from the VPN client CIDR (10.200.0.0/16). Even though users can connect to the VPN, the security group acts as a virtual firewall for the endpoint; without an inbound rule permitting traffic from the client CIDR, packets from clients are dropped before they can be routed to VPC resources. The question states that the security group allows inbound traffic from 'the VPN clients' but not specifically from the client CIDR range, which is a common misconfiguration.

Answer

The Client VPN endpoint's authentication is failing.

Answer

The VPN endpoint is not associated with the correct subnet.

Answer

The route table in VPC A does not have a route for the Client VPN CIDR.

Question 19

A company has a Direct Connect connection with a private VIF to a VPC. The on-premises router is advertising a default route (0.0.0.0/0) via BGP. The VPC has an internet gateway attached, and the route table has a default route to the internet gateway. The network team notices that traffic from on-premises to the internet is not working as expected. What is the most likely cause?

Accepted Answer

The on-premises router is advertising a default route, causing a routing conflict.. The on-premises router advertising a default route (0.0.0.0/0) via BGP over the private VIF causes a routing conflict because the VPC route table already has a default route pointing to the internet gateway. When traffic from on-premises destined for the internet enters the VPC, it matches the more specific BGP-learned default route and is forwarded back toward the on-premises router (or black-holed), rather than being sent to the internet gateway. This creates a routing loop or asymmetric routing, breaking internet connectivity from on-premises.

Answer

The BGP session is not established.

Answer

The VPC route table does not have a route to the internet gateway for the on-premises traffic.

Answer

The private VIF is associated with the wrong VLAN.

Question 20

A company has deployed a web application in a VPC with public subnets for the web servers and private subnets for the database servers. The web servers need to access the internet for software updates. The network engineer configured a NAT Gateway in the public subnet and added a route in the private subnet route table pointing 0.0.0.0/0 to the NAT Gateway. However, the web servers cannot reach the internet. What is the most likely cause?

Accepted Answer

The web servers are in a public subnet, but the route table for the public subnet points 0.0.0.0/0 to the NAT Gateway instead of the Internet Gateway.. Option C is correct because the web servers are deployed in a public subnet, which requires a route table entry pointing 0.0.0.0/0 to an Internet Gateway (IGW) for direct internet access. Instead, the engineer configured the route to point to a NAT Gateway, which is intended for private subnets. A public subnet must have a direct IGW route; using a NAT Gateway in a public subnet breaks outbound connectivity because the NAT Gateway itself relies on the IGW for internet access, but the web servers' traffic is sent to the NAT Gateway instead of the IGW, causing a routing loop or failure.

Answer

The private subnet route table does not have a route to the NAT Gateway for 0.0.0.0/0.

Answer

The security group of the web servers is blocking outbound traffic to the internet.

Answer

The NAT Gateway does not have a route to the Internet Gateway in its route table.