Amazon Application Recovery Controller (ARC) currently supports the following resources for zonal shift and zonal autoshift:
Application Load Balancers with cross-zone load balancing enabled or disabled
Network Load Balancers with cross-zone load balancing enabled or disabled
For specific requirements for Network Load Balancers and Application Load Balancers, see the additional topics in this section.
Review the following conditions for working with zonal shifts, zonal autoshift, and resources in ARC:
A resource must be active and fully provisioned to shift traffic for it. Before you start a zonal shift for a resource, check to make sure that it's a managed resource in ARC. For example, view the list of managed resources in the AWS Management Console, or use the
get-managed-resourceoperation with the resource's identifier.To start a zonal shift with a resource, it must be deployed in the Availability Zone and AWS Region where you start the shift. Make sure that you start a zonal shift in the same Region that the AZ you want to shift away from is in, and that the resource that you're shifting traffic for is in the same AZ and Region as well.
Ensure that you have the correct IAM permissions to use zonal shift with a resource. For more information, see IAM and permissions for zonal shift.
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When a Network Load Balancer or Application Load Balancer is in a fail open state zonal shift will have no effect. This is expected behavior because zonal shift cannot force an AZ to be unhealthy and then shift traffic to the other AZs in a Region when the load balancer is failing open. For more information, refer to the Using Route 53 DNS failover for your load balancer in the Network Load Balancers User Guide and Using Route 53 DNS failover for your load balancer in the Application Load Balancers User Guide.
If multiple load balancers are forwarding traffic to the same targets, a zonal shift on a cross zone enabled load balancer will drop target capacity for all load balancers, even if they are not zonal shifted.
