Route 53 Zonal Shift with ALB Target Group Settings

DOP-C02 By islever Editorial Last updated

Manage event sources to process, notify, and take action in response to events.

Short answer

B Disable cross-zone load balancing on the target group and use Route 53 ARC to start a zonal shift.

Question

A company has an application that runs on Amazon EC2 instances behind an Application Load Balancer (ALB). The EC2 instances are in multiple Availability Zones. The application was misconfigured in a single Availability Zone, which caused a partial outage of the application.
A DevOps engineer made changes to ensure that the unhealthy EC2 instances in one Availability Zone do not affect the healthy EC2 instances in the other Availability Zones. The DevOps engineer needs to test the application's failover and shift where the ALB sends traffic. During failover, the ALB must avoid sending traffic to the Availability Zone where the failure has occurred.
Which solution will meet these requirements?
  1. Turn off cross-zone load balancing on the ALB. Use Amazon Route 53 Application Recovery Controller to start a zonal shift away from the Availability Zone.
  2. Turn off cross-zone load balancing on the ALB’s target group. Use Amazon Route 53 Application Recovery Controller to start a zonal shift away from the Availability Zone. Correct Answer
  3. Create an Amazon Route 53 Application Recovery Controller resource set that uses the DNS hostname of the ALB. Start a zonal shift for the resource set away from the Availability Zone.
  4. Create an Amazon Route 53 Application Recovery Controller resource set that uses the ARN of the ALB’s target group. Create a readiness check that uses the ElbV2TargetGroupsCanServeTraffic rule.

Key Takeaways

Tests knowledge of specific prerequisites for Route 53 ARC zonal shifts: cross-zone load balancing must be disabled at the target group, not the ALB level.

Learn how to perform a zonal shift for an Application Load Balancer by disabling cross-zone load balancing at the target group level and using Route 53 Application Recovery Controller.

Common mistake: Choosing Option A because it incorrectly states that cross-zone load balancing can be turned off at the ALB level, which is technically impossible for ALBs.

Expert Analysis

Why the Answer Is Correct

Option B is correct because Amazon Route 53 Application Recovery Controller's zonal shift feature requires cross-zone load balancing to be disabled. For Application Load Balancers (ALBs), this setting is configured at the Target Group level, not the ALB level. Disabling it at the target group ensures traffic is only routed to healthy instances within the same Availability Zone, allowing the zonal shift to effectively isolate the failure. Using ARC to start a zonal shift then redirects DNS traffic away from the affected zone.

Why the Other Options Are Wrong

Option A is incorrect because you cannot turn off cross-zone load balancing on an ALB itself; it is always enabled at the ALB level. Options C and D are incorrect because they do not address the prerequisite configuration (disabling cross-zone load balancing at the target group) required for the zonal shift to work as intended without affecting healthy zones.

Community Comment Notes

Community consensus strongly favors Option B. Users like Chris12722222 and Shenannigan pointed out that "You can not turn of cross-zone load balancing on an ALB" but can do so at the target group level. Several users initially leaned toward A due to confusion about where the setting resides, but documentation confirms the target group is the correct scope.

Official Reference

These links open the official vendor documentation in a new tab.

Exam Strategy

Always verify the granularity of service configurations. For AWS services like ALBs, settings often exist at different levels (e.g., LB vs. Target Group). Memorize that ARC zonal shifts require cross-zone load balancing to be disabled specifically at the target group for ALBs.

Frequently Asked Questions

Can I disable cross-zone load balancing on an ALB directly?

No, cross-zone load balancing is always enabled for ALBs. You must disable it at the Target Group level.

Why does ARC need cross-zone load balancing disabled?

It ensures traffic stays in the healthy zone during a shift, preventing the ALB from sending requests to unhealthy instances in other zones.

More DOP-C02 FAQ →

Discussion 17 contributions

Compiled from public community threads and reader submissions, lightly edited for clarity. Handles and vote tallies are shown as recorded, and comments reflect the views of individual contributors.

From public community threads 17

  1. inturist 👍 7 Answered A
    For me the correct answer is A:"Note that the Elastic Load Balancing resources must have cross-zone load balancing turned off to use this capability." https://docs.aws.amazon.com/r53recovery/latest/dg/arc-zonal-shift.html
  2. Shenannigan 👍 4 Answered B
    Answer is B You can not turn of cross-zone load balancing on an ALB: https://docs.aws.amazon.com/elasticloadbalancing/latest/application/application-load-balancers.html#cross-zone-load-balancing You can turn it off at the Target Group: https://aws.amazon.com/about-aws/whats-new/2022/11/application-load-balancers-turning-off-cross-zone-load-balancing-per-target-group/ zonal shift: https://docs.aws.amazon.com/elasticloadbalancing/latest/userguide/how-elastic-load-balancing-works.html#cross-zone-load-balancing#:~:text=zonal%20shift
  3. CHRIS12722222 👍 4 Answered B
    Cant turn off cross zone load balancing at ALB level
  4. jamesf 👍 3 Answered A
    - Turning off cross-zone load balancing on the ALB ensures that each Availability Zone only handles traffic directed to its own healthy instances, allowing for granular control over traffic distribution. This prevents the ALB from sending traffic to the unhealthy instances across all zones, thereby isolating the problem to the affected zone. - Amazon Route 53 Application Recovery Controller's Zonal Shifts is used to direct traffic away from a specific AZ that experiences a failure, allowing the ALB to reroute requests to healthy AZs automatically. Amazon Route 53 Application Recovery Controller currently supports the following resources for zonal shift and zonal autoshift: - Network Load Balancers with cross-zone load balancing disabled - Application Load Balancers with cross-zone load balancing disabled https://docs.aws.amazon.com/r53recovery/latest/dg/arc-zonal-shift.resource-types.html
  5. limelight04 👍 2 Answered A
    A is the most appropriate answer due to the reasons below; Option A: Turning off cross-zone load balancing on the ALB and using Amazon Route 53 Application Recovery Controller to start a zonal shift away from the affected Availability Zone ensures that traffic is not sent to the unhealthy instances in the problematic zone. This directly addresses the need to avoid sending traffic to the Availability Zone where the failure has occurred. Option D: While creating a resource set and readiness check with Amazon Route 53 Application Recovery Controller is useful for monitoring and ensuring traffic is routed to healthy instances, it doesn’t explicitly mention turning off cross-zone load balancing, which is crucial for isolating the affected Availability Zone.
Show 12 more comments
  1. trungtd 👍 2 Answered C
    A&B Turn off cross-zone load balancing is a bad idea D involves creating a readiness check rule (ElbV2TargetGroupsCanServeTraffic) which checks the ability of the ALB’s target groups to serve traffic. However, this does not directly control traffic routing based on Availability Zone health. C Route 53 Application Recovery Controller: It directly manages traffic based on health checks and allows for zonal shifts Zonal Shift: Specifically addresses the requirement to avoid sending traffic to an Availability Zone experiencing issues
  2. jamesf 👍 2
    B Incorrect: This option mentions turning off cross-zone load balancing on the ALB's target group rather than the ALB itself. This does not apply because cross-zone load balancing is a property of the ALB, not the target group. This makes the solution nonviable because the configuration settings described do not exist on target groups.
  3. spring21 👍 2 Answered B
    To turn off cross-zone load balancing on an Application Load Balancer (ALB), you cannot directly disable it at the ALB level; instead, you need to modify the target group settings and explicitly disable cross-zone load balancing within the target group attributes
  4. bgc1 👍 2 Answered B
    For ALB, you can only turn off cross zone at target group level - https://docs.aws.amazon.com/elasticloadbalancing/latest/userguide/how-elastic-load-balancing-works.html#:~:text=The%20nodes%20for%20your%20load,zone%20load%20balancing%20is%20disabled:
  5. chinchin97 👍 1 Answered B
    Turning off cross-zone load balancing at the target group level ensures that each target group handles traffic independently for its specific Availability Zone. Why specifically target group is because cross-zone load balancing is always turned on and cannot be turned off for a ALB. But, if using target group, the default is to use the load balancer setting, which you can override the default by explicitly turning cross-zone load balancing off at the target group level. The next part us to move away from the affected region by using Amazon Route 53 Application Recovery Controller. Option A works well for a ELB, but for ALB, you can't turn off cross-zone load balancing. Option C is good to handle DNS failover, but doesn't stop traffic from going to the affected zone. Option D doesn't handle moving of traffic away from the affected zone and add extra complexity by introducing a readiness check.
  6. nickp84 👍 1 Answered A
    The statement is incorrect because cross-zone load balancing for an Application Load Balancer (ALB) is configured at the ALB level, not the target group level. To meet the requirements from the previous question: Disable cross-zone load balancing on the ALB using the load_balancing.cross_zone.enabled=false attribute to isolate traffic to each AZ, ensuring unhealthy instances in one AZ do not receive traffic (assuming health checks mark them unhealthy). Use Amazon Route 53 Application Recovery Controller to start a zonal shift to redirect ALB traffic away from the affected AZ during failover testing. The correct solution remains Option A
  7. Exto1124 👍 1
    "With Application Load Balancers, cross-zone load balancing is always turned on at the load balancer level, and cannot be turned off. For target groups, the default is to use the load balancer setting, but you can override the default by explicitly turning cross-zone load balancing off at the target group level." https://docs.aws.amazon.com/elasticloadbalancing/latest/application/disable-cross-zone.html#:~:text=The%20nodes%20for%20your%20load,in%20all%20registered%20Availability%20Zones.
  8. elivan_coelho 👍 1 Answered B
    For me the correct answer is B: "You can turn on cross-zone load balancing for your Application Load Balancer target groups at any time. The cross-zone load balancing setting at the target group level overrides the setting at the load balancer level." B is corret https://docs.aws.amazon.com/elasticloadbalancing/latest/application/edit-target-group-attributes.html#cross_zone_console_disable
  9. Rs123x 👍 1 Answered C
    This solution leverages Amazon Route 53 Application Recovery Controller to initiate a zonal shift and ensures that traffic is redirected away from the failing Availability Zone while keeping the ALB in operation.
  10. BelloMio 👍 1 Answered B
    It's B because question 304 has it on the target group. 'Turn off cross-zone load balancing on the ALB’s target group'
  11. garupy 👍 1 Answered B
    answer is B
  12. jojewi8143 👍 1 Answered A
    i choose a

Reader comments & corrections

No reader corrections yet — spotted an error or have a note? Share it below.

Log in to comment, report an error, or add a note about this question.

Optimizing Amazon Timestream Query Performance

S-grade

Deploy the CloudWatch agent as a StatefulSet with IRSA and CloudWatchAgentServerPolicy, and configure the OIDC provider

S-grade

Disable cross-zone load balancing on the target group and start an Application Recovery Controller zonal shift

S-grade

Stream all CloudWatch metrics to Firehose, transform with Lambda, and deliver to S3

S-grade

Practice All DOP-C02 Questions

Access 85 questions with complete answers and detailed explanations.

View Full DOP-C02 Practice Test →

← Back to DOP-C02 Study Guide