# Capacity reservations for your Network Load Balancer Load balancer Capacity Unit (LCU) reservations allow you to reserve a static minimum capacity for your load balancer. Network Load Balancers automatically scale to support detected workloads and meet capacity needs. When minimum capacity is configured, your load balancer continues scaling up or down based on the traffic received, but also prevents the capacity from going lower than the minimum capacity configured. Consider using LCU reservation in following situations: + You have an upcoming event that will have a sudden, unusual high traffic and want to ensure your load balancer can support the sudden traffic spike during the event. + You have unpredictable spiky traffic due to the nature of your workload for a short period. + You are setting up your load balancer to on-board or migrate your services at a specific start time and need start with a high capacity instead of waiting for auto-scaling to take effect. + You are migrating workloads between load balancers and want to configure the destination to match the scale of the source. **Estimate the capacity that you need** When determining the amount of capacity you should reserve for your load balancer, we recommend performing load testing or reviewing historical workload data that represents the upcoming traffic you expect. Using the Elastic Load Balancing console, you can estimate how much capacity you need to reserve based on the reviewed traffic. Alternatively, you can refer to CloudWatch metric **ProcessedBytes** to determine the right level of capacity. Capacity for your load balancer is reserved in LCUs, with each LCU being equal to 2.2Mbps. You can use the Max (**ProcessedBytes**) metric to see the maximum per-minute throughput traffic on the load balancer, then convert that throughput to LCUs using a conversion rate of 2.2Mbps equals 1 LCU. If you don't have historical workload data to reference and cannot perform load testing, you can estimate capacity needed using the LCU reservation calculator. The LCU reservation calculator uses data based on historical workloads AWS observe and may not represent your specific workload. For more information, see [Load Balancer Capacity Unit Reservation Calculator](https://exampleloadbalancer.com/ondemand_capacity_reservation_calculator.html). **Supported Regions** This feature is available only in the following Regions: + US East (N. Virginia) + US East (Ohio) + US West (Oregon) + Asia Pacific (Hong Kong) + Asia Pacific (Singapore) + Asia Pacific (Sydney) + Asia Pacific (Tokyo) + Europe (Frankfurt) + Europe (Ireland) + Europe (Stockholm) **Minimum and maximum values for an LCU reservation** The total reservation request must be at least 2,750 LCU per Availability Zone. The maximum value is determined by the quotas for your account. For more information, see [Load Balancer Capacity Units](load-balancer-limits.md#lcu-quotas). # Request Load balancer Capacity Unit reservation for your Network Load Balancer Before you use LCU reservation, review the following: + LCU reservation is not supported on Network Load Balancers using TLS listeners. + LCU reservation only supports reserving throughput capacity for Network Load Balancers. When requesting a LCU reservation, convert your capacity needs from Mbps to LCUs using the conversion rate of 1 LCU to 2.2 Mbps. + Capacity is reserved at the regional level and is evenly distributed across availability zones. Confirm you have enough evenly distributed targets in each availability zone before turning on LCU reservation. + LCU reservation requests are fulfilled on a first come first serve basis, and depends on available capacity for a zone at that time. Most requests are typically fulfilled within an hour, but can take up to a few hours. + To update an existing reservation, the previous request must be provisioned or failed. You can increase reserved capacity as many times as you need, however you can only decrease the reserved capacity two times per day. + You will continue to incur charges for any reserved or provisioned capacity until they are terminated or cancelled. ------ #### [ Console ] **To request an LCU reservation** 1. Open the Amazon EC2 console at [https://console.aws.amazon.com/ec2/](https://console.aws.amazon.com/ec2/). 1. On the navigation pane, choose **Load Balancers**. 1. Select the load balancer name. 1. On the **Capacity** tab, choose **Edit LCU Reservation**. 1. Select **Historic reference based estimate**. 1. Select the reference period to view the recommended reserved LCU level. 1. If you do not have historic reference workload, you can choose **Manual estimate** and enter the number of LCUs to be reserved. 1. Choose **Save**. ------ #### [ AWS CLI ] **To request an LCU reservation** Use the [modify-capacity-reservation](https://docs.aws.amazon.com/cli/latest/reference/elbv2/modify-capacity-reservation.html) command. ``` aws elbv2 modify-capacity-reservation \ --load-balancer-arn load-balancer-arn \ --minimum-load-balancer-capacity CapacityUnits=3000 ``` ------ #### [ CloudFormation ] **To request an LCU reservation** Update the [AWS::ElasticLoadBalancingV2::LoadBalancer](https://docs.aws.amazon.com/AWSCloudFormation/latest/TemplateReference/aws-resource-elasticloadbalancingv2-loadbalancer.html) resource. ``` Resources: myLoadBalancer: Type: 'AWS::ElasticLoadBalancingV2::LoadBalancer' Properties: Name: my-alb Type: application Scheme: internal Subnets: - !Ref subnet-AZ1 - !Ref subnet-AZ2 SecurityGroups: - !Ref mySecurityGroup MinimumLoadBalancerCapacity: CapacityUnits: 3000 ``` ------ # Update or cancel Load Balancer Capacity Unit reservations for your Network Load Balancer If the traffic patterns for your load balancer change, you can update or cancel the LCU reservation for your load balancer. ------ #### [ Console ] **To update or cancel an LCU reservation** 1. Open the Amazon EC2 console at [https://console.aws.amazon.com/ec2/](https://console.aws.amazon.com/ec2/). 1. On the navigation pane, choose **Load Balancers**. 1. Select the load balancer name. 1. On the **Capacity** tab, do one of the following: 1. To update the LCU reservation choose **Edit LCU Reservation**. 1. To cancel the LCU reservation, choose **Cancel Capacity**. ------ #### [ AWS CLI ] **To cancel an LCU reservation** Use the [modify-capacity-reservation](https://docs.aws.amazon.com/cli/latest/reference/elbv2/modify-capacity-reservation.html) command. ``` aws elbv2 modify-capacity-reservation \ --load-balancer-arn load-balancer-arn \ --reset-capacity-reservation ``` ------ # Monitor Load balancer Capacity Unit reservation for your Network Load Balancer **Reservation status** The following are the possible status values for an LCU reservation: + `pending` ‐ Indicates the reservation it is in the process of provisioning. + `provisioned` ‐ Indicates the reserved capacity is ready and available to use. + `failed` ‐ Indicates the request cannot be completed at the time. + `rebalancing` ‐ Indicates an availability zone has been added or removed and the load balancer is rebalancing capacity. **LCU utilization** To determine reserved LCU utilization, you can compare the per-minute `ProcessedBytes` metric with the per-hour `Sum(ReservedLCUs)`. To convert bytes per minute to LCU per hour, use (bytes per min)\$18/60/ (10^6)/2.2. ------ #### [ Console ] **To view the status of an LCU reservation** 1. Open the Amazon EC2 console at [https://console.aws.amazon.com/ec2/](https://console.aws.amazon.com/ec2/). 1. On the navigation pane, choose **Load Balancers**. 1. Select the load balancer name. 1. On the **Capacity** tab, you can view the **Reservation Status** and **Reserved LCU** value. ------ #### [ AWS CLI ] **To monitor the status of an LCU reservation** Use the [describe-capacity-reservation](https://docs.aws.amazon.com/cli/latest/reference/elbv2/describe-capacity-reservation.html) command. ``` aws elbv2 describe-capacity-reservation \ --load-balancer-arn load-balancer-arn ``` ------