AWS Network Load Balancer now supports removing availability zones

Today, we are launching the ability to remove Availability Zones (AZ) of an existing Network Load Balancer (NLB). Prior to this launch, customers could add AZs to an existing NLB, but could not remove AZs. With this capability, customers can now change their application stack locations and move them between availability zones quickly.

Changing business needs such as mergers & acquisitions, divestitures, data residency compliance requirements, and capacity considerations in a given region are some of the use cases that necessitate removing AZs of existing NLBs. Using this capability, customers can remove one or more availability zones from their NLB by simply updating the list of enabled subnets using ELB API, CLI or Console.

Similar to any delete operation, removing a zone can be a potentially disruptive operation. When you remove a zone, the NLB zonal Elastic Network Interface (ENI) is deleted. All active connections to backend targets in that zone (including clients connecting through other zones) are terminated, the zonal IPs (and EIPs) are released and zonal DNS names deleted, and any backend target in the removed zone becomes “unused”. Refer to product documentation and AWS blog post for prescriptive guidance on how to use this capability in a safe manner.

This capability is available in all AWS commercial and the AWS GovCloud (US) Regions.