# Zonal shift for your Network Load Balancer Zonal shift is a capability in Amazon Application Recovery Controller (ARC). With zonal shift, you can shift a Network Load Balancer resource away from an impaired Availability Zone with a single action. This way, you can continue operating from other healthy Availability Zones in an AWS Region. When you start a zonal shift, your Network Load Balancer stops routing traffic to targets in the affected Availability Zone. Existing connections to targets in the affected Availability Zone are not terminated by zonal shift. It might take several minutes for these connections to complete gracefully. **Topics** + [Before you begin](#zonal-shift-before-you-begin) + [Administrative override](#admin-override) + [Enable zonal shift](enable-zonal-shift.md) + [Start a zonal shift](start-zonal-shift.md) + [Update a zonal shift](update-zonal-shift.md) + [Cancel a zonal shift](cancel-zonal-shift.md) ## Before you begin a zonal shift + Zonal shift is disabled by default and must be enabled on each Network Load Balancer. For more information, see [Enable zonal shift for your Network Load Balancer](enable-zonal-shift.md). + You can start a zonal shift for a specific Network Load Balancer only for a single Availability Zone. You can't start a zonal shift for multiple Availability Zones. + AWS proactively removes zonal Network Load Balancer IP addresses from DNS when multiple infrastructure issues impact services. Always check current Availability Zone capacity before you start a zonal shift. If you use a zonal shift on your Network Load Balancer, the Availability Zone affected by the zonal shift also loses target capacity. + During zonal shift on Network Load Balancers with cross-zone load balancing enabled, the zonal load balancer IP addresses are removed from DNS. Existing connections to targets in the impaired Availability Zone persist until they organically close, while new connections are no longer routed to targets in the impaired Availability Zone. For more information, see [Best practices for zonal shifts in ARC](https://docs.aws.amazon.com/r53recovery/latest/dg/route53-arc-best-practices.zonal-shifts.html) in the *Amazon Application Recovery Controller (ARC) Developer Guide*. ## Zonal shift administrative override Targets that belong to a Network Load Balancer will include a new status `AdministrativeOverride`, which is independent from the `TargetHealth` state. When a zonal shift is started for a Network Load Balancer, all targets within the zone being shifted away from are considered administratively overridden. The Network Load Balancer stops routing new traffic to administratively overridden targets. Existing connections remain intact until they are organically closed. The possible `AdministrativeOverride` states are: **unknown** State cannot be propagated due to an internal error **no\$1override** No override is currently active on target **zonal\$1shift\$1active** Zonal shift is active in target Availability Zone **zonal\$1shift\$1delegated\$1to\$1dns** This target's zonal shift state is not available through `DescribeTargetHealth` but can be viewed directly through the AWS ARC - Zonal Shift API or console. # Enable zonal shift for your Network Load Balancer Zonal shift is disabled by default and must be enabled on each Network Load Balancer. This ensures that you can start a zonal shift using only the specific Network Load Balancers that you want. For more information, see [Zonal shift for your Network Load Balancer](zonal-shift.md). **Prerequisites** If you enable cross-zone load balancing for the load balancer, every target group attached to the load balancer must meet the following requirements before you can enable zonal shift. + The target group protocol must be `TCP` or `TLS`. + The target group type must not be `alb`. + [Connection termination for unhealthy targets](edit-target-group-attributes.md#unhealthy-target-connection-termination) must be disabled. + The `load_balancing.cross_zone.enabled` target group attribute must be `true` or `use_load_balancer_configuration` (the default). ------ #### [ Console ] **To enable zonal shift** 1. Open the Amazon EC2 console at [https://console.aws.amazon.com/ec2/](https://console.aws.amazon.com/ec2/). 1. On the navigation pane, under **Load Balancing**, choose **Load Balancers**. 1. Select the Network Load Balancer. 1. On the **Attributes** tab, choose **Edit**. 1. Under **Availability Zone routing configuration**, for **ARC zonal shift integration**, choose **Enable**. 1. Choose **Save changes**. ------ #### [ AWS CLI ] **To enable zonal shift** Use the [modify-load-balancer-attributes](https://docs.aws.amazon.com/cli/latest/reference/elbv2/modify-load-balancer-attributes.html) command with the `zonal_shift.config.enabled` attribute. ``` aws elbv2 modify-load-balancer-attributes \ --load-balancer-arn load-balancer-arn \ --attributes "Key=zonal_shift.config.enabled,Value=true" ``` ------ #### [ CloudFormation ] **To enable zonal shift** Update the [AWS::ElasticLoadBalancingV2::LoadBalancer](https://docs.aws.amazon.com/AWSCloudFormation/latest/TemplateReference/aws-resource-elasticloadbalancingv2-loadbalancer.html) resource to include the `zonal_shift.config.enabled` attribute. ``` Resources: myLoadBalancer: Type: 'AWS::ElasticLoadBalancingV2::LoadBalancer' Properties: Name: my-nlb Type: network Scheme: internal Subnets: - !Ref subnet-AZ1 - !Ref subnet-AZ2 SecurityGroups: - !Ref mySecurityGroup LoadBalancerAttributes: -Key: "zonal_shift.config.enabled" Value: "true" ``` ------ # Start a zonal shift for your Network Load Balancer Zonal shift in ARC enables you to temporarily move traffic for supported resources away from an Availability Zone so that your application can continue to operate normally with other Availability Zones in an AWS Region. **Prerequisite** Before you begin, verify that you [enabled zonal shift](enable-zonal-shift.md#enable-zonal-shift.title) for the load balancer. ------ #### [ Console ] This procedure explains how to start a zonal shift using the Amazon EC2 console. For steps to start a zonal shift using the ARC console, see [Starting a zonal shift](https://docs.aws.amazon.com/r53recovery/latest/dg/arc-zonal-shift.start-cancel.html) in the *Amazon Application Recovery Controller (ARC) Developer Guide*. **To start a zonal shift** 1. Open the Amazon EC2 console at [https://console.aws.amazon.com/ec2/](https://console.aws.amazon.com/ec2/). 1. On the navigation pane, under **Load Balancing**, choose **Load Balancers**. 1. Select the Network Load Balancer. 1. On the **Integrations** tab, expand **Amazon Application Recovery Controller (ARC)** and choose **Start zonal shift**. 1. Select the Availability Zone that you want to move traffic away from. 1. Choose or enter an expiration for the zonal shift. A zonal shift can initially be set from 1 minute up to three days (72 hours). All zonal shifts are temporary. You must set an expiration, but you can update active shifts later to set a new expiration. 1. Enter a comment. You can update the zonal shift later to edit the comment. 1. Select the check box to acknowledge that starting a zonal shift reduces capacity for your application by shifting traffic away from the Availability Zone. 1. Choose **Confirm**. ------ #### [ AWS CLI ] **To start a zonal shift** Use the Amazon Application Recovery Controller (ARC) [start-zonal-shift](https://docs.aws.amazon.com/cli/latest/reference/arc-zonal-shift/start-zonal-shift.html) command. ``` aws arc-zonal-shift start-zonal-shift \ --resource-identifier load-balancer-arn \ --away-from use2-az2 \ --expires-in 2h \ --comment "zonal shift due to scheduled maintenance" ``` ------ # Update a zonal shift for your Network Load Balancer You can update a zonal shift to set a new expiration, or edit or replace the comment for the zonal shift. ------ #### [ Console ] This procedure explains how to update a zonal shift using the Amazon EC2 console. For steps to update a zonal shift using the Amazon Application Recovery Controller (ARC) console, see [Updating a zonal shift](https://docs.aws.amazon.com/r53recovery/latest/dg/arc-zonal-shift.start-cancel.html) in the *Amazon Application Recovery Controller (ARC) Developer Guide*. **To update a zonal shift** 1. Open the Amazon EC2 console at [https://console.aws.amazon.com/ec2/](https://console.aws.amazon.com/ec2/). 1. On the navigation pane, under **Load Balancing**, choose **Load Balancers**. 1. Select an Application Load Balancer with an active zonal shift. 1. On the **Integrations** tab, expand **Amazon Application Recovery Controller (ARC)** and choose **Update zonal shift**. This opens the ARC console to continue the update process. 1. (Optional) For **Set zonal shift expiration**, select or enter an expiration. 1. (Optional) For **Comment**, optionally edit the existing comment or enter a new comment. 1. Choose **Update**. ------ #### [ AWS CLI ] **To update a zonal shift** Use the Amazon Application Recovery Controller (ARC) [update-zonal-shift](https://docs.aws.amazon.com/cli/latest/reference/arc-zonal-shift/update-zonal-shift.html) command. ``` aws arc-zonal-shift update-zonal-shift \ --zonal-shift-id 9ac9ec1e-1df1-0755-3dc5-8cf57EXAMPLE \ --expires-in 1h \ --comment "extending zonal shift for scheduled maintenance" ``` ------ # Cancel a zonal shift for your Network Load Balancer You can cancel a zonal shift any time before it expires. You can cancel zonal shifts that you initiate, or zonal shifts that AWS starts for a resource for a practice run for zonal autoshift. ------ #### [ Console ] This procedure explains how to cancel a zonal shift using the Amazon EC2 console. For steps to cancel a zonal shift using the Amazon Application Recovery Controller (ARC) console, see [Canceling a zonal shift](https://docs.aws.amazon.com/r53recovery/latest/dg/arc-zonal-shift.start-cancel.html) in the *Amazon Application Recovery Controller (ARC) Developer Guide*. **To cancel a zonal shift** 1. Open the Amazon EC2 console at [https://console.aws.amazon.com/ec2/](https://console.aws.amazon.com/ec2/). 1. On the navigation pane, under **Load Balancing**, choose **Load Balancers**. 1. Select a Network Load Balancer with an active zonal shift. 1. On the **Integrations** tab, under **Amazon Application Recovery Controller (ARC)**, choose **Cancel zonal shift**. This opens the ARC console to continue the cancelation process. 1. Choose **Cancel zonal shift**. 1. When prompted for confirmation, choose **Confirm**. ------ #### [ AWS CLI ] **To cancel a zonal shift** Use the Amazon Application Recovery Controller (ARC) [cancel-zonal-shift](https://docs.aws.amazon.com/cli/latest/reference/arc-zonal-shift/cancel-zonal-shift.html) command. ``` aws arc-zonal-shift cancel-zonal-shift \ --zonal-shift-id 9ac9ec1e-1df1-0755-3dc5-8cf57EXAMPLE ``` ------