Subnets for Redshift resources
You create a subnet group if you are creating a provisioned cluster in a virtual private
cloud (VPC). Each VPC can have one or more subnets, which are subsets of IP addresses within
the VPC that enable you to group resources based on your security and operation needs. You
create a subnet group to specify a set of subnets in your VPC when you create a provisioned
cluster. In the Provisioned clusters dashboard, you can find and edit
cluster subnet groups under Configurations. During initial configuration
for a provisioned cluster, you specify the subnet group and Amazon Redshift creates the cluster in
one of its subnets. For more information about the VPC service, see the Amazon VPC
Subnet configuration for an Amazon Redshift Serverless workgroup is similar to a provisioned cluster, but the steps differ slightly. When you create and set up a Serverless workgroup, you specify subnets for the workgroup, and they're added to a list. You can view the subnets for an existing workgroup by selecting the workgroup properties, in the Serverless dashboard. They're available in the Network and security properties. For more information, see Creating a workgroup with a namespace.
For more information about creating a VPC, go to Amazon VPC User Guide documentation.
After creating a subnet group for a provisioned cluster, or choosing subnets for a Serverless workgroup, it's possible to remove subnets previously added or to add more. You can make these changes using the console, or using API operations. For more information regarding API operations for a provisioned cluster, see ModifyClusterSubnetGroup. For API operations for a Serverless workgroup, see UpdateWorkgroup.
You can provision a cluster on one of the subnets in the subnet group. A cluster subnet group enables you to specify a set of subnets in your virtual private cloud (VPC).
Warning
During cluster maintenance operations such as classic resize, pause and resume, Multi-AZ failovers, or other events, your provisioned compute nodes might be moved to another subnet within your Amazon Redshift cluster subnet group. Note that all subnets in a subnet group must have the same Network ACL inbound and outbound rules and the same route-table routes. This ensures connectivity to and from the Amazon Redshift compute resources, so they can communicate and function optimally after such maintenance events. Avoid adding subnets with varying network ACL or route-table configurations to the same Amazon Redshift cluster subnet group.
For more information about configuring subnets, see Subnets for your VPC in the Amazon VPC user guide. For more information about Redshift Multi-AZ deployments, see Multi-AZ deployment in the Redshift management guide. Resizing a cluster is also covered in the Redshift management guide.