Creating a subnet group - Amazon ElastiCache for Redis
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Creating a subnet group

A cache subnet group is a collection of subnets that you may want to designate for your cache clusters in a VPC. When launching a cache cluster in a VPC, you need to select a cache subnet group. Then ElastiCache uses that cache subnet group to assign IP addresses within that subnet to each cache node in the cluster.

When you create a new subnet group, note the number of available IP addresses. If the subnet has very few free IP addresses, you might be constrained as to how many more nodes you can add to the cluster. To resolve this issue, you can assign one or more subnets to a subnet group so that you have a sufficient number of IP addresses in your cluster's Availability Zone. After that, you can add more nodes to your cluster.

If you choose IPV4 as your network type, a default subnet group will be available or you can choose to create a new one. ElastiCache uses that subnet group to choose a subnet and IP addresses within that subnet to associate with your nodes. If you choose dual-stack or IPV6, you will be directed to create dual-stack or IPV6 subnets. For more information on network types, see Choosing a network type. For more information, see Create a subnet in your VPC.

The following procedures show you how to create a subnet group called mysubnetgroup (console), the Amazon CLI, and the ElastiCache API.

Creating a subnet group (Console)

The following procedure shows how to create a subnet group (console).

To create a subnet group (Console)
  1. Sign in to the Amazon Management Console, and open the ElastiCache console at

  2. In the navigation list, choose Subnet Groups.

  3. Choose Create Subnet Group.

  4. In the Create Subnet Group wizard, do the following. When all the settings are as you want them, choose Yes, Create.

    1. In the Name box, type a name for your subnet group.

    2. In the Description box, type a description for your subnet group.

    3. In the VPC ID box, choose the Amazon VPC that you created.

    4. In the Availability Zone and Subnet ID lists, choose the Availability Zone or Local Zone and ID of your private subnet, and then choose Add.

									Image: Create Subnet VPC screen
  5. In the confirmation message that appears, choose Close.

Your new subnet group appears in the Subnet Groups list of the ElastiCache console. At the bottom of the window you can choose the subnet group to see details, such as all of the subnets associated with this group.

Creating a subnet group (Amazon CLI)

At a command prompt, use the command create-cache-subnet-group to create a subnet group.

For Linux, OS X, or Unix:

aws elasticache create-cache-subnet-group \ --cache-subnet-group-name mysubnetgroup \ --cache-subnet-group-description "Testing" \ --subnet-ids subnet-53df9c3a

For Windows:

aws elasticache create-cache-subnet-group ^ --cache-subnet-group-name mysubnetgroup ^ --cache-subnet-group-description "Testing" ^ --subnet-ids subnet-53df9c3a

This command should produce output similar to the following:

{ "CacheSubnetGroup": { "VpcId": "vpc-37c3cd17", "CacheSubnetGroupDescription": "Testing", "Subnets": [ { "SubnetIdentifier": "subnet-53df9c3a", "SubnetAvailabilityZone": { "Name": "us-west-2a" } } ], "CacheSubnetGroupName": "mysubnetgroup" } }

For more information, see the Amazon CLI topic create-cache-subnet-group.

Creating a subnet group (ElastiCache API)

Using the ElastiCache API, call CreateCacheSubnetGroup with the following parameters:

  • CacheSubnetGroupName=mysubnetgroup

  • CacheSubnetGroupDescription==Testing

  • SubnetIds.member.1=subnet-53df9c3a

Example ?Action=CreateCacheSubnetGroup &CacheSubnetGroupDescription=Testing &CacheSubnetGroupName=mysubnetgroup &SignatureMethod=HmacSHA256 &SignatureVersion=4 &SubnetIds.member.1=subnet-53df9c3a &Timestamp=20141201T220302Z &Version=2014-12-01 &X-Amz-Algorithm=&AWS;4-HMAC-SHA256 &X-Amz-Credential=<credential> &X-Amz-Date=20141201T220302Z &X-Amz-Expires=20141201T220302Z &X-Amz-Signature=<signature> &X-Amz-SignedHeaders=Host