Amazon AWS Certified Advanced Networking — Specialty ANS-C01 Exam Dumps and Practice Test Questions Set11 Q151-165

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Question 151: 

An organization is deploying a highly available web application across three Availability Zones using an Application Load Balancer. The application requires that client requests from the same user session are always routed to the same backend instance to maintain session state. However, if that instance becomes unhealthy, requests should be routed to another instance. Which ALB feature should be configured to meet this requirement?

A) Path-based routing rules to direct requests to specific target groups

B) Sticky sessions with application-based cookie duration

C) Cross-zone load balancing to distribute traffic evenly across zones

D) Connection draining to gracefully handle unhealthy instances

Answer: B

Explanation:

Sticky sessions, also known as session affinity, with application-based cookie duration is the appropriate ALB feature for ensuring that requests from the same user session are routed to the same backend instance. When sticky sessions are enabled, the Application Load Balancer generates a cookie that is sent to the client. This cookie contains information about which target instance should handle subsequent requests from that client. As long as the client includes this cookie in future requests and the target instance remains healthy, the ALB will route all requests to the same instance, maintaining session state.

Application Load Balancers support two types of sticky sessions: duration-based cookies generated by the load balancer, and application-based cookies generated by the application itself. For most scenarios, the load balancer-generated duration-based cookie is sufficient and simpler to implement. The cookie duration can be configured from one second to seven days, depending on how long you want sessions to persist. This approach works transparently without requiring application modifications, as the ALB automatically manages cookie generation and session routing.

Option A is incorrect because path-based routing directs requests to different target groups based on the URL path in the request, not based on which client is making the request. This feature is used for microservices architectures where different paths need to be routed to different backend services, but it doesn’t provide session affinity to specific instances.

Option C is incorrect because cross-zone load balancing affects how traffic is distributed across Availability Zones, ensuring even distribution even when there are different numbers of targets in each zone. It does not provide any session affinity or ensure that requests from the same user go to the same instance.

Option D is incorrect because connection draining is a feature that allows in-flight requests to complete when an instance is being deregistered or becomes unhealthy. While important for graceful shutdowns, it doesn’t provide session affinity or route requests from the same user to the same instance.

Question 152: 

A company is running a legacy application that requires source IP address visibility for security logging and compliance purposes. The application is deployed behind a Network Load Balancer in AWS. However, the application servers are only seeing the Network Load Balancer’s private IP addresses as the source of incoming connections, not the original client IP addresses. What configuration change should be made to preserve client IP addresses?

A) Enable Proxy Protocol v2 on the Network Load Balancer and configure the application to parse it

B) Configure the Network Load Balancer to use UDP protocol instead of TCP

C) Disable cross-zone load balancing to maintain direct client connections

D) Create a target group with target type set to IP addresses instead of instances

Answer: A

Explanation:

Enabling Proxy Protocol version 2 on the Network Load Balancer and configuring the application to parse it is the correct solution for preserving client IP addresses when connection termination is performed by the load balancer. By default, when a Network Load Balancer operates in certain configurations, particularly with TLS termination or when targets are specified by instance ID, the source IP address seen by the target is the private IP address of the load balancer node, not the original client’s IP address. This behavior is problematic for applications that need the original client IP for security, logging, or compliance requirements.

Option B is incorrect because changing from TCP to UDP protocol doesn’t address the source IP preservation issue and would fundamentally change how the application communicates. Additionally, not all applications can use UDP, and this change would require application modifications. UDP listeners on NLB do preserve source IP by default, but switching protocols isn’t a viable solution for existing TCP applications.

Option C is incorrect because cross-zone load balancing affects traffic distribution across Availability Zones but does not impact source IP address preservation. Disabling cross-zone load balancing would not expose the original client IP addresses to the targets.

Option D is incorrect because changing the target type to IP addresses instead of instances doesn’t inherently solve the source IP preservation problem. While IP target types can be useful in some architectures, they don’t automatically preserve client IP addresses when the NLB is performing connection handling. Proxy Protocol is still needed regardless of target type.

Question 153: 

A financial services company requires that all network traffic between their on-premises data center and AWS be encrypted and traverse only dedicated, private connections. They cannot use the public internet for any communication with AWS. The company also needs to access both VPC resources and AWS public services like S3 and DynamoDB. Which combination of AWS services should be implemented?

A) AWS Direct Connect with a private virtual interface only

B) AWS Direct Connect with both private and public virtual interfaces

C) Site-to-Site VPN over Direct Connect using a transit virtual interface

D) AWS Direct Connect with a private virtual interface and VPC endpoints for AWS services

Answer: D

Explanation:

AWS Direct Connect with a private virtual interface combined with VPC endpoints for AWS services is the optimal solution that meets all requirements while ensuring traffic never traverses the public internet. Direct Connect provides a dedicated private connection between the on-premises data center and AWS, eliminating reliance on the public internet. The private virtual interface enables access to resources within VPCs using private IP addresses, which is essential for connecting to EC2 instances, RDS databases, and other VPC-hosted resources.

Option A is incorrect because a private virtual interface alone only provides access to resources within VPCs using private IP addresses. It does not enable access to AWS public services like S3 and DynamoDB. The company would have no way to access these essential AWS services without either using a public virtual interface or implementing VPC endpoints.

Option B is incorrect because a public virtual interface routes traffic to AWS public services over AWS’s network, but this traffic technically uses public IP addresses and AWS’s public-facing service endpoints. While the traffic doesn’t traverse the general internet and stays within AWS’s network, it doesn’t provide the same level of isolation as accessing services through VPC endpoints with private IP addresses.

Option C is incorrect because while a transit virtual interface is used with Direct Connect Gateway for routing traffic to multiple VPCs across regions or accounts, it doesn’t specifically address the requirement for accessing AWS public services privately. Additionally, running VPN over Direct Connect adds unnecessary complexity and encryption overhead when Direct Connect itself provides a private dedicated connection.

Question 154: 

A company’s network team is implementing IPv6 support for their existing IPv4-based VPC infrastructure. The VPC currently hosts production applications that must remain accessible via IPv4 during the migration. The team needs to enable IPv6 while ensuring backward compatibility and minimal disruption. What is the correct approach to implement dual-stack networking in the VPC?

A) Replace the existing IPv4 CIDR block with an IPv6 CIDR block

B) Associate an IPv6 CIDR block with the VPC while retaining the existing IPv4 CIDR

C) Create a new VPC with IPv6 CIDR and migrate resources using VPC peering

D) Configure IPv6 addresses only on new instances and keep existing instances on IPv4

Answer: B

Explanation:

Associating an IPv6 CIDR block with the VPC while retaining the existing IPv4 CIDR block is the correct approach for implementing dual-stack networking. AWS VPCs support dual-stack operation, allowing resources to communicate using both IPv4 and IPv6 addresses simultaneously. This approach provides backward compatibility, ensuring that existing IPv4 communications continue to function without interruption while enabling new IPv6 connectivity. The migration can be performed gradually, testing IPv6 functionality while maintaining full IPv4 support.

When you associate an IPv6 CIDR block with a VPC, AWS automatically assigns a /56 CIDR block from Amazon’s pool of IPv6 addresses. You can then assign /64 CIDR blocks from this range to individual subnets within the VPC. Instances launched in these subnets can be assigned both IPv4 and IPv6 addresses automatically, depending on subnet configuration. The routing infrastructure in the VPC supports both protocol versions simultaneously, with separate route table entries for IPv4 destinations and IPv6 destinations. Internet Gateways support both protocols, allowing dual-stack instances to communicate with the internet using either IP version.

Option A is incorrect because you cannot simply replace an IPv4 CIDR block with an IPv6 CIDR block. VPCs require an IPv4 CIDR block at creation, and this cannot be removed. Additionally, replacing rather than adding would immediately break all existing IPv4 communications, causing complete service disruption. IPv4 and IPv6 are meant to coexist in a dual-stack configuration, not replace each other.

Option C is incorrect because creating an entirely new VPC and migrating resources is unnecessarily complex and disruptive. This approach would require recreating all network infrastructure, reconfiguring applications, updating DNS records, and coordinating a complex migration. AWS’s support for dual-stack VPCs eliminates the need for such drastic measures.

Option D is incorrect because the approach described in this option is not a deliberate architecture decision but rather a consequence of not properly configuring the VPC for dual-stack operation. To properly implement IPv6, you must associate an IPv6 CIDR block with the VPC and subnets. Simply assigning IPv6 addresses to some instances while leaving others on IPv4 without proper VPC configuration would not provide full dual-stack functionality.

Question 155: 

A media streaming company is experiencing high data transfer costs for content delivered from their AWS infrastructure to users. The content consists of large video files stored in S3, accessed by users globally. The company wants to reduce data transfer costs while maintaining good performance for users. What is the most cost-effective solution?

A) Enable S3 Transfer Acceleration for faster uploads and downloads

B) Deploy Amazon CloudFront as a CDN to cache content at edge locations

C) Use VPC endpoints for S3 to avoid data transfer charges

D) Implement S3 Intelligent-Tiering to automatically move files to cheaper storage classes

Answer: B

Explanation:

Deploying Amazon CloudFront as a Content Delivery Network to cache content at edge locations is the most cost-effective solution for reducing data transfer costs while maintaining performance for global users. CloudFront significantly reduces data transfer costs because once content is cached at an edge location, subsequent requests for that content are served directly from the edge location rather than being retrieved from the origin S3 bucket. This dramatically reduces data transfer out charges from S3, which are typically much higher than CloudFront’s edge-to-user data transfer costs.

Option A is incorrect because S3 Transfer Acceleration is designed to speed up uploads to S3 and can also accelerate downloads, but it does not reduce data transfer costs. In fact, Transfer Acceleration incurs additional charges on top of standard S3 costs. While it improves transfer speeds by routing data through CloudFront edge locations, each download still results in data transfer from S3, incurring full data transfer charges.

Option C is incorrect because VPC endpoints for S3 are used to enable private connectivity between a VPC and S3 without traversing the internet. While VPC endpoints eliminate data transfer costs for traffic between EC2 instances and S3 within the same region, they don’t help with delivering content to external users globally. The question specifically addresses content delivery to users, not internal AWS resource communication.

Option D is incorrect because S3 Intelligent-Tiering optimizes storage costs by automatically moving objects between access tiers based on access patterns, but it doesn’t reduce data transfer costs. Data transfer out charges are incurred regardless of which storage tier the content resides in. While Intelligent-Tiering is valuable for reducing storage costs, it doesn’t address the primary concern of data transfer costs for frequently accessed content.

Question 156: 

A company operates a distributed application with components running in multiple VPCs across different AWS accounts and regions. The application requires low-latency, high-throughput connectivity between all components. The network architecture should allow any component to communicate with any other component, and the solution should be scalable as new VPCs are added. What is the most scalable solution?

A) Full mesh of VPC peering connections between all VPCs

B) AWS Transit Gateway in each region with inter-region peering between Transit Gateways

C) Site-to-Site VPN connections between each pair of VPCs

D) AWS PrivateLink endpoints for each service in every VPC

Answer: B

Explanation:

AWS Transit Gateway in each region with inter-region peering between Transit Gateways provides the most scalable and manageable solution for connecting multiple VPCs across accounts and regions with full mesh connectivity. Transit Gateway operates as a cloud router that allows transitive routing between all attached networks, meaning any VPC attached to a Transit Gateway can communicate with any other attached VPC without requiring direct connections between each pair. This dramatically simplifies network architecture compared to alternatives like VPC peering.

Option A is incorrect because a full mesh of VPC peering connections does not scale effectively. The number of required peering connections grows quadratically with the number of VPCs. For N VPCs, you would need N×(N-1)/2 peering connections. With even 50 VPCs, this results in 1,225 peering connections, which becomes unmanageable. Additionally, each account has limits on the number of VPC peering connections, and managing route tables across hundreds of peering connections is operationally complex.

Option C is incorrect because Site-to-Site VPN connections are designed for connecting on-premises networks to AWS, not for inter-VPC connectivity. Creating VPN connections between each pair of VPCs would be extremely complex, expensive, and would introduce unnecessary encryption overhead for traffic that remains within the AWS network.

Option D is incorrect because PrivateLink endpoints are designed for exposing specific services from one VPC to others, not for general network connectivity between VPCs. Each service would need its own endpoint configured in each consuming VPC, and this approach does not provide the general network connectivity required for a distributed application where any component needs to reach any other component.

Question 157: 

A security team requires that all network traffic to and from EC2 instances be logged for compliance and forensic analysis. The logs must include information about source and destination IP addresses, ports, protocols, packet counts, and whether traffic was accepted or rejected. The solution should have minimal performance impact on applications. Which AWS feature should be implemented?

A) VPC Flow Logs published to CloudWatch Logs or S3

B) VPC Traffic Mirroring to capture full packet data

C) AWS CloudTrail to log all API calls related to network resources

D) Amazon GuardDuty for network anomaly detection

Answer: A

Explanation:

VPC Flow Logs published to CloudWatch Logs or S3 is the appropriate solution for capturing network traffic metadata for compliance and forensic analysis. VPC Flow Logs capture information about IP traffic going to and from network interfaces in your VPC. The logs include critical details such as source and destination IP addresses, source and destination ports, protocol numbers, packet and byte counts, action taken, and timestamp information. This metadata is exactly what’s required for compliance logging and forensic investigation of network-related security incidents.

VPC Flow Logs operate at the network interface level and can be enabled at different scopes: for specific network interfaces, for entire subnets, or for entire VPCs. The logs capture both accepted and rejected traffic, providing visibility into what traffic is being permitted or denied by security groups and network ACLs. This is valuable for troubleshooting connectivity issues and verifying that security controls are functioning as intended. Flow Logs can be configured to capture all traffic, only accepted traffic, or only rejected traffic, allowing you to customize logging based on your specific requirements.

The key advantage of VPC Flow Logs for this use case is the minimal performance impact. Flow Logs are collected and published asynchronously, outside the path of your network traffic, so they do not affect network throughput or latency. There is no agent to install or additional infrastructure to manage—Flow Logs are a native VPC feature that operates transparently. Logs can be published to CloudWatch Logs for real-time analysis and alerting, or to S3 for long-term storage and batch analysis. For compliance requirements, S3 storage with appropriate lifecycle policies provides cost-effective long-term retention.

Option B is incorrect because VPC Traffic Mirroring captures full packet data, not just metadata. While this provides the most comprehensive visibility, it generates enormous volumes of data and requires significant storage and processing infrastructure to analyze. For compliance and general forensic analysis, the metadata captured by Flow Logs is typically sufficient, making Traffic Mirroring unnecessarily complex and expensive for this requirement.

Option C is incorrect because CloudTrail logs API calls made to AWS services, not network traffic. CloudTrail would record actions like creating security groups or modifying network ACLs, but it does not capture information about actual network packets flowing between instances. CloudTrail is complementary to VPC Flow Logs but does not fulfill the requirement for network traffic logging.

Option D is incorrect because Amazon GuardDuty is a threat detection service that analyzes various data sources including VPC Flow Logs to identify potentially malicious activity. While GuardDuty uses Flow Logs as one of its data sources, it does not itself provide the raw traffic logs required for compliance. GuardDuty focuses on threat detection rather than comprehensive traffic logging.

Question 158: 

A company is deploying a new application that requires accessing AWS services from EC2 instances in private subnets without any internet exposure. The instances should not have public IP addresses, and all communication with AWS services must remain within the AWS network. The application needs to access S3, DynamoDB, and Systems Manager. What is the most cost-effective solution?

A) Deploy NAT Gateways in each Availability Zone for instances to access AWS services

B) Configure gateway endpoints for S3 and DynamoDB, and interface endpoints for Systems Manager

C) Use AWS PrivateLink with interface endpoints for all three services

D) Establish a Direct Connect connection to access AWS services privately

Answer: B

Explanation:

Configuring gateway endpoints for S3 and DynamoDB combined with interface endpoints for Systems Manager is the most cost-effective solution that meets all requirements. This approach leverages two different types of VPC endpoints, each optimized for different AWS services. Gateway endpoints are available for S3 and DynamoDB and are completely free with no hourly charges or data processing charges. Interface endpoints, powered by AWS PrivateLink, are available for many AWS services including Systems Manager, and while they do incur hourly charges, they provide the necessary private connectivity for services that don’t support gateway endpoints.

Gateway endpoints work by adding routes to VPC route tables that direct traffic destined for S3 or DynamoDB to the gateway endpoint instead of to an Internet Gateway or NAT Gateway. This traffic remains entirely within the AWS network and never traverses the internet. The gateway endpoint appears as a target in your route table, similar to how an Internet Gateway appears. There are no additional resources deployed in your VPC, and there are no charges for using gateway endpoints, making them the most cost-effective option for accessing S3 and DynamoDB.

Option A is incorrect because NAT Gateways, while they would enable the instances to reach AWS services, route traffic to the internet and are more expensive than VPC endpoints. NAT Gateways incur both hourly charges and data processing charges for all traffic passing through them. Additionally, traffic through NAT Gateways goes to the public endpoints of AWS services, which technically traverses AWS’s internet-facing infrastructure even though it doesn’t leave AWS’s network.

Option C is incorrect because while you could use interface endpoints for all three services, this approach is unnecessarily expensive. Interface endpoints charge both hourly fees and data processing fees. Since S3 and DynamoDB support free gateway endpoints, there’s no reason to use more expensive interface endpoints for these services when gateway endpoints provide the same private connectivity at no cost.

Option D is incorrect because Direct Connect is designed for connecting on-premises data centers to AWS, not for enabling EC2 instances within AWS to access AWS services. Direct Connect is expensive and complex to implement, and it’s completely unnecessary for the use case described, where all resources are already within AWS.

Question 159: 

A company’s application uses Network Load Balancers to distribute traffic to EC2 instances across multiple Availability Zones. During a recent incident, the application experienced downtime when all instances in one Availability Zone simultaneously failed health checks due to a misconfigured deployment. The company wants to implement a solution that prevents traffic from being sent to an Availability Zone if all targets in that zone are unhealthy. What NLB feature addresses this requirement?

A) Enable connection draining to gracefully handle unhealthy targets

B) Configure cross-zone load balancing to distribute traffic across all zones

C) Disable cross-zone load balancing so each zone’s load balancer node only targets instances in its own zone

D) Enable zonal shift to temporarily move traffic away from an impaired Availability Zone

Answer: D

Explanation:

Enabling zonal shift capability allows operators to temporarily move traffic away from an Availability Zone that is experiencing impairments. Zonal shift is a feature that works with Network Load Balancers and Application Load Balancers to provide rapid response to Availability Zone failures. When initiated, a zonal shift directs the load balancer to stop sending traffic to targets in the specified Availability Zone and instead distribute that traffic to targets in other healthy zones. This prevents customers from experiencing errors when an entire zone’s targets become unhealthy.

Zonal shift is particularly valuable for scenarios like the one described, where an operational issue such as a misconfigured deployment causes all instances in an Availability Zone to fail simultaneously. Rather than relying solely on individual target health checks, which might cause the load balancer to continue attempting connections to the impaired zone, zonal shift provides a way to proactively remove an entire zone from service. The shift can be configured with a specific duration, after which traffic automatically resumes to the zone, or it can be cancelled early if the issue is resolved sooner.

The feature integrates with AWS observability services and can be monitored through CloudWatch metrics, allowing you to see when zonal shifts are active and track their impact on traffic distribution. Zonal shift requires that your application is deployed in at least two Availability Zones with sufficient capacity in each zone to handle the redistributed traffic. It’s an important component of a resilient architecture because it acknowledges that despite best efforts, entire Availability Zone failures can occur, whether due to operational mistakes, infrastructure problems, or other unexpected events.

Option A is incorrect because connection draining helps gracefully handle individual targets that are being deregistered or that become unhealthy, allowing existing connections to complete before the target is fully removed from service. However, it does not prevent new connections from being sent to an Availability Zone where all targets are unhealthy.

Option B is incorrect because enabling cross-zone load balancing would actually exacerbate the problem. With cross-zone load balancing enabled, load balancer nodes in healthy Availability Zones would continue sending traffic to the unhealthy zone, spreading the impact of the failure across all users rather than containing it.

Option C is incorrect because disabling cross-zone load balancing only ensures that each load balancer node sends traffic to targets in its own Availability Zone. This doesn’t solve the problem of what happens when all targets in a zone are unhealthy—users connecting through that zone’s load balancer node would still experience failures. Additionally, disabling cross-zone load balancing can lead to uneven traffic distribution if Availability Zones have different numbers of targets.

Question 160: 

A global enterprise is implementing a disaster recovery strategy for their AWS infrastructure spanning multiple regions. The network architecture must support automatic failover of application traffic from the primary region to the secondary region when the primary region becomes unavailable. The failover should happen within one minute, and DNS propagation delays must be minimized. Which AWS service provides the fastest failover for this requirement?

A) Amazon Route 53 with health checks and failover routing policy

B) AWS Global Accelerator with health checks on endpoint groups

C) Amazon CloudFront with multiple origin servers and origin failover

D) Elastic Load Balancing with cross-region target groups

Answer: B

Explanation:

AWS Global Accelerator with health checks on endpoint groups provides the fastest failover capability for disaster recovery scenarios across regions. Global Accelerator continuously monitors the health of application endpoints using health checks and can detect failures within seconds. When an endpoint becomes unhealthy, Global Accelerator automatically routes traffic to healthy endpoints in other regions, typically completing failover within 30 seconds or less. This is significantly faster than DNS-based failover solutions because Global Accelerator operates at the network layer rather than relying on DNS resolution and caching.

Global Accelerator performs continuous health checks on your endpoint groups, which represent application endpoints in different regions. You can configure health check parameters including protocol, port, path, and check intervals. When Global Accelerator detects that all endpoints in a region are unhealthy, it immediately begins routing traffic to endpoints in other regions that are healthy. The health check results are used in real-time for routing decisions, ensuring that traffic is never sent to failed endpoints. Combined with its anycast IP addresses that don’t require DNS updates, Global Accelerator provides the fastest and most reliable failover mechanism for multi-region architectures.

Option A is incorrect because while Route 53 health checks and failover routing can automate disaster recovery, DNS-based failover is subject to DNS caching delays. Even with very low TTL values, many DNS resolvers and clients don’t respect TTL perfectly, and it can take several minutes or longer for all clients to receive updated DNS records pointing to the secondary region. This makes it difficult to achieve failover within one minute consistently.

Option C is incorrect because CloudFront with origin failover is designed for failover between multiple origins for content delivery, not for application-level disaster recovery. CloudFront’s failover is automatic when the primary origin fails, but CloudFront is a CDN service optimized for content delivery, not for providing general application failover across regions. Additionally, CloudFront’s failover behavior is designed for origin server failures, not for regional failures.

Option D is incorrect because Elastic Load Balancing does not support cross-region target groups. Load balancers operate within a single region and can only distribute traffic to targets within that region. While you can deploy load balancers in multiple regions, routing traffic between regions for disaster recovery purposes requires a higher-level service like Global Accelerator or Route 53.

Question 161: 

A company has implemented AWS Direct Connect for hybrid cloud connectivity. They are experiencing intermittent connectivity issues, and the network team suspects packet loss on the Direct Connect connection. The team needs to monitor the connection’s performance metrics to identify the issue. Which metrics should they review to diagnose packet loss and performance degradation?

A) ConnectionState, ConnectionBpsEgress, and ConnectionBpsIngress metrics

B) ConnectionLightLevelTx, ConnectionLightLevelRx, and ConnectionErrorCount metrics

C) VirtualInterfaceByesIn, VirtualInterfacePacketsIn, and VirtualInterfaceBytesOut metrics

D) Direct Connect gateway attachments and route propagation status

Answer: B

Explanation:

ConnectionLightLevelTx, ConnectionLightLevelRx, and ConnectionErrorCount metrics are the most relevant CloudWatch metrics for diagnosing physical layer issues including packet loss on Direct Connect connections. These metrics provide visibility into the health of the physical connection itself, which is often the root cause of intermittent connectivity problems. Light level metrics measure the signal strength of the optical connection and can indicate physical problems with fiber optic cables, transceivers, or connections that may not be severe enough to cause complete link failure but can result in packet loss and performance degradation.

ConnectionLightLevelTx and ConnectionLightLevelRx measure the transmitted and received optical signal strength in dBm for fiber connections. If these values are outside the acceptable range for your transceiver type, it indicates physical problems that can cause intermittent packet loss. Low light levels might indicate dirty fiber connectors, damaged fiber, excessive cable length, or failing transceivers. High light levels, while less common, can also cause issues by saturating the receiver. AWS provides expected light level ranges in the Direct Connect documentation, and values outside these ranges should be investigated and typically require physical intervention.

ConnectionErrorCount tracks the number of times the Direct Connect connection has encountered errors at the physical or data link layer. Incrementing error counts, even if the connection state remains up, indicate underlying problems that may manifest as packet loss, jitter, or temporary connectivity disruptions. Common causes include physical layer problems, hardware issues with routers or switches, or configuration mismatches such as MTU size discrepancies. By monitoring these metrics over time and correlating error counts with user-reported issues, network teams can identify patterns that help pinpoint the root cause.

Option A is incorrect because while ConnectionState indicates whether the connection is up or down, and ConnectionBpsEgress/Ingress show bandwidth utilization, these metrics don’t directly indicate packet loss or physical layer problems. High bandwidth utilization might suggest congestion, but it doesn’t identify the specific issues causing packet loss, especially when loss is intermittent and not correlated with high traffic volumes.

Option C is incorrect because VirtualInterface metrics measure traffic at the virtual interface layer, which is a logical abstraction above the physical connection. While these metrics show whether traffic is flowing, they don’t provide insights into physical layer health or error rates. You could see normal byte and packet counts even while experiencing quality issues that affect application performance.

Option D is incorrect because Direct Connect Gateway attachments and route propagation status are configuration elements that affect connectivity and reachability, but they don’t provide performance metrics that would indicate packet loss. These elements are typically either working or not working, rather than exhibiting gradual performance degradation.

Question 162: 

A financial institution must ensure that all data in transit between their application servers and database servers is encrypted to meet regulatory compliance requirements. The application and database servers are deployed in the same VPC across multiple Availability Zones. The database is Amazon RDS for PostgreSQL. What is the appropriate method to encrypt data in transit for this connection?

A) Enable VPC Traffic Mirroring with encryption enabled

B) Configure application servers to connect to RDS using SSL/TLS with the require_ssl parameter enabled

C) Enable EBS encryption on both application and database server volumes

D) Configure VPN connections between application and database security groups

Answer: B

Explanation:

Configuring application servers to connect to RDS using SSL/TLS with the require_ssl parameter enabled is the correct method for encrypting data in transit between application servers and databases. Amazon RDS supports SSL/TLS encryption for connections to database instances, providing industry-standard encryption for data in transit. For PostgreSQL, you configure the database to require SSL connections by setting the rds.force_ssl parameter to 1 in the parameter group, which ensures that all client connections must use SSL/TLS encryption. On the application side, you configure the database connection string to use SSL mode and provide the RDS certificate.

The implementation involves several steps: first, modify the RDS parameter group to enable the rds.force_ssl parameter; second, download the RDS certificate authority certificate bundle from AWS; third, configure your application’s database connection library to use SSL mode and reference the CA certificate; and finally, verify that connections are encrypted by checking connection status in the database. Most database client libraries support SSL/TLS connections natively and simply require configuration parameters to enable encryption.

This approach provides strong encryption for data in transit using industry-standard protocols without requiring changes to the network infrastructure or introducing performance-impacting encryption overhead at the network layer. SSL/TLS encryption is performed by the database client and server, making it transparent to the underlying network. The encryption protects data from being intercepted or read if network traffic is somehow captured, meeting regulatory requirements for data protection. Certificate-based authentication can also be implemented for additional security, ensuring that clients are connecting to the legitimate RDS instance.

Option A is incorrect because VPC Traffic Mirroring is a monitoring tool that copies network traffic from network interfaces for analysis by security and monitoring appliances. It does not encrypt traffic between application and database servers. Traffic Mirroring is used for visibility and inspection, not for securing communications.

Option C is incorrect because EBS encryption protects data at rest on storage volumes, not data in transit over the network. While EBS encryption is an important security control and should be enabled, it does not address the requirement for encrypting data as it travels between application servers and database servers over the network.

Option D is incorrect because you cannot configure VPN connections between security groups. VPN connections are established between networks, such as between on-premises networks and AWS, not between individual resources or security groups within AWS. Additionally, for resources within the same VPC, VPN encryption would be unnecessary overhead when application-layer SSL/TLS provides the required encryption.

Question 163: 

A company operates a multi-tier application with web servers in public subnets and application servers in private subnets. The application servers need to make outbound HTTPS connections to external APIs on the internet, but they should not be directly accessible from the internet. The solution should provide high availability across multiple Availability Zones. What is the most appropriate architecture?

A) Assign Elastic IP addresses to application servers and use security groups to restrict inbound access

B) Deploy NAT Gateways in multiple Availability Zones and configure route tables to route internet traffic through them

C) Create VPC peering to another VPC that has internet access and route traffic through it

D) Use an Internet Gateway with restrictive security groups on application servers

Answer: B

Explanation:

Deploying NAT Gateways in multiple Availability Zones and configuring route tables to route internet traffic through them is the correct architecture for enabling outbound internet connectivity for instances in private subnets while maintaining high availability. NAT Gateway is a managed AWS service that provides network address translation, allowing instances with private IP addresses to initiate outbound connections to the internet while preventing unsolicited inbound connections from the internet. This meets the requirement for application servers to access external APIs without being directly reachable from the internet.

For high availability, best practices recommend deploying a NAT Gateway in each Availability Zone where you have private subnets with resources that need internet access. Each private subnet’s route table is configured with a route directing internet-destined traffic to the NAT Gateway in the same Availability Zone. This architecture ensures that if one Availability Zone becomes unavailable, resources in other zones can continue accessing the internet through their local NAT Gateways. The cross-AZ failure isolation is critical because if you deployed only a single NAT Gateway, all internet-bound traffic from private subnets across all Availability Zones would route through that one zone, creating both a bandwidth bottleneck and a single point of failure.

NAT Gateway is a fully managed service with built-in high availability within an Availability Zone, capable of scaling automatically to accommodate bandwidth requirements up to 45 Gbps. It provides better performance and reliability compared to NAT instances, which require manual configuration and management. The NAT Gateway itself is deployed in a public subnet and must be associated with an Elastic IP address, which serves as the source IP for outbound connections. Security is maintained because the NAT Gateway only allows connections initiated from the private subnet and does not accept unsolicited inbound connections from the internet.

Option A is incorrect because assigning Elastic IP addresses to application servers places them directly on the internet with public IP addresses. Even with security groups restricting inbound access, this configuration violates the principle of least exposure and increases the attack surface. Application servers should remain in private subnets without public IP addresses, using NAT Gateway for outbound connectivity.

Option C is incorrect because VPC peering is not designed for internet access and would not provide the network address translation needed for private subnet instances to access the internet. VPC peering creates direct connectivity between two VPCs, but neither VPC can use the other’s Internet Gateway. You cannot route internet traffic through a peered VPC to reach the internet.

Option D is incorrect because instances must have public IP addresses to use an Internet Gateway directly. Internet Gateways provide bidirectional connectivity between the internet and resources with public IP addresses, but they cannot provide outbound-only access for private IP addresses. Using an Internet Gateway requires instances to have public IPs, which would make them directly accessible from the internet, contradicting the requirement.

Question 164: 

A company is migrating their on-premises applications to AWS and needs to maintain the same private IP address ranges they currently use for internal communication. Their on-premises network uses 10.0.0.0/8, and several legacy applications are hardcoded with IP addresses in this range. The migration plan involves gradually moving applications to AWS while maintaining connectivity between on-premises and cloud environments. What should the network architect consider when planning the VPC CIDR blocks?

A) Use the same 10.0.0.0/8 CIDR block for the VPC to maintain IP address consistency

B) Use a non-overlapping CIDR block for the VPC and implement NAT to translate between address spaces

C) Split the 10.0.0.0/8 range between on-premises and AWS, using different subnets from the same range

D) Use IPv6 addressing in AWS to avoid IP address conflicts

Answer: C

Explanation:

Splitting the 10.0.0.0/8 range between on-premises and AWS environments, using different subnets from the same overall address space, is the most practical approach for this migration scenario. This strategy allows the company to carve out specific subnets within their existing 10.0.0.0/8 range for use in AWS VPCs while keeping other subnets for on-premises use. For example, they might allocate 10.0.0.0/16 through 10.10.0.0/16 for AWS VPCs and reserve 10.11.0.0/16 through 10.255.0.0/16 for on-premises use, ensuring the subnets don’t overlap between the two environments.

This approach is particularly important for hybrid cloud architectures where connectivity between on-premises and AWS is maintained through Direct Connect or VPN connections. When using these connectivity methods, the on-premises network and AWS VPCs must have non-overlapping IP address spaces for routing to function correctly. If both environments use the same subnet ranges, routers cannot determine whether an IP address refers to an on-premises resource or an AWS resource, causing routing failures and connectivity problems.

The key to successful implementation is careful IP address management and planning. Before creating VPCs, the company should document which subnets are currently in use on-premises and which are available for allocation to AWS. They should allocate appropriately sized CIDR blocks to AWS VPCs based on growth projections, remembering that you cannot modify a VPC’s CIDR block after creation, though you can add secondary CIDR blocks. For legacy applications with hardcoded IP addresses, you can potentially rehost them in AWS using the same specific IP addresses they used on-premises, as long as those IP addresses fall within the subnet range allocated to the appropriate AWS VPC.

Option A is incorrect because using the exact same CIDR block for both on-premises and AWS environments creates overlapping IP address spaces, which makes routing impossible. When you connect the on-premises network to AWS via Direct Connect or VPN, the routers need to distinguish between addresses in each location, which is impossible with overlapping ranges.

Option B is incorrect because while using a completely non-overlapping CIDR block would work from a routing perspective, implementing NAT to translate addresses adds significant complexity and can break applications that rely on seeing actual source IP addresses. NAT also introduces performance overhead and complicates troubleshooting. Given that the company has a large private address space available, properly partitioning it is simpler than implementing translation.

Option D is incorrect because moving to IPv6 in AWS would require rewriting or reconfiguring the legacy applications that are hardcoded for IPv4, defeating the purpose of maintaining address consistency during migration. While IPv6 might be part of a long-term modernization strategy, it doesn’t address the immediate need to maintain compatibility with IPv4-based legacy applications.

Question 165: 

A development team has created a web application that must be accessible only from specific corporate IP addresses. The application is deployed on EC2 instances behind an Application Load Balancer. Security requirements mandate that the ALB should reject requests from any IP address outside the approved list. What is the most appropriate way to implement this IP-based access control?

A) Configure security groups on the ALB to allow traffic only from corporate IP addresses

B) Implement AWS WAF with an IP set match rule attached to the ALB

C) Use network ACLs on the ALB’s subnets to block unauthorized IP addresses

D) Configure Route 53 routing policies to resolve the domain only for corporate IP addresses

Answer: B

Explanation:

Implementing AWS WAF with an IP set match rule attached to the Application Load Balancer is the most appropriate and effective way to implement IP-based access control at the application layer. AWS WAF is a web application firewall that integrates directly with Application Load Balancers, allowing you to create rules that inspect incoming requests and allow or block them based on various criteria including source IP addresses. IP set match rules in WAF allow you to create a list of IP address ranges and define whether requests from those addresses should be allowed or blocked.

Option A is incorrect because while security groups do support IP-based rules, security groups on ALBs have limitations that make them less suitable for this use case. Security groups have a limit on the number of rules, and managing a large list of corporate IP addresses as individual security group rules quickly becomes unwieldy. Additionally, security groups operate at the network layer rather than the application layer, providing less flexibility for web application access control.

Option C is incorrect because network ACLs are not practical for implementing IP allowlists with many addresses. Network ACLs have a limit of 20 rules per ACL (inbound and outbound combined), and rules are evaluated in numerical order. With potentially dozens or hundreds of corporate IP addresses, you would quickly exceed this limit. Additionally, network ACLs are stateless and require rules for both inbound requests and outbound responses, doubling the rule count needed.

Option D is incorrect because Route 53 routing policies control where DNS queries are resolved but cannot enforce IP-based access control. DNS responses are provided to any client that queries the domain, and nothing prevents unauthorized clients from using the resolved IP address to access the application directly, bypassing any DNS-based restrictions.