[AWS] How to create multiple private subnets with different names in VPC module

Terraform Providers AWS
1

Hi,

I was using this module Terraform Registry

I want to create private subnets without using keywords such as database_subnets or elasticache_subnets, but for some reason terraform gives me this error: Error: creating EC2 VPC: InvalidParameterValue: The allocation size is too big for the pool. status code: 400, request id: 4b211e71-05f7-474c-90f3-ef3f43e4a3ba

this is the code: main.tf

module "vpc" {
  source            = "terraform-aws-modules/vpc/aws"
  ipv4_ipam_pool_id = data.aws_vpc_ipam_pool.ipv4_prod.id
  cidr              = data.aws_vpc_ipam_preview_next_cidr.previewed_cidr.cidr
  private_subnets   = local.cidrsubnet_private
  public_subnets    = local.cidrsubnet_public
  name              = local.vpc_name

  azs = local.azs

  # For every value of numbers of AZ, join the AZ name with subnet name
  public_subnet_names  = [for value in local.azs : join("-", [value, local.public_subnet_name])]
  private_subnet_names = local.private_subnets_all_names
}

locals:

locals {
  partition          = cidrsubnets(data.aws_vpc_ipam_preview_next_cidr.previewed_cidr.cidr, 1, 2, 3, 3) # result = 3 Sub CIDRs with prefixes 25, 26, 27, 27
  cidrsubnet_public  = cidrsubnets(local.partition[2], 1, 1)                                         # Result = 1 Sub CIDR with prefix 28
  cidrsubnet_wld     = cidrsubnets(local.partition[0], 1, 1)                                         # Result = 1 Sub CIDR with prefix 26
  cidrsubnet_data    = cidrsubnets(local.partition[1], 1, 1)                                         # Result = 1 Sub CIDR with prefix 27
  cidrsubnet_tgw     = cidrsubnets(local.partition[3], 1, 1)                                         # Result = 1 Sub CIDR with prefix 28
  azs                = formatlist("${data.aws_region.current.name}%s", ["a", "b"])
  cidrsubnet_private = tolist(concat(local.cidrsubnet_wld, local.cidrsubnet_data, local.cidrsubnet_tgw))
}

# Reusable local variables for VPC module
locals {
  vpc_name           = "xxxxxx"
  public_subnet_name = "public_subnet"
}

# List of multiple private subnet names
locals {
  private_subnet_workload_name = [for value in local.azs : join("-", [value, "workload_subnet"])]
  private_subnet_datatier_name = [for value in local.azs : join("-", [value, "datatier_subnet"])]
  private_subnet_tgw_name      = [for value in local.azs : join("-", [value, "transit_gateway_subnet"])]
  private_subnets_all_names    = tolist(concat(local.private_subnet_workload_name, local.private_subnet_datatier_name, local.private_subnet_tgw_name))
}

but when adding the additional resources such as database_subnets or elasticache_subnets it works.

module "vpc" {
  source              = "terraform-aws-modules/vpc/aws"
  ipv4_ipam_pool_id   = data.aws_vpc_ipam_pool.ipv4_prod.id
  cidr                = data.aws_vpc_ipam_preview_next_cidr.previewed_cidr.cidr
  database_subnets    = local.cidrsubnet_data
  elasticache_subnets = local.cidrsubnet_tgw
  private_subnets     = local.cidrsubnet_wld
  public_subnets      = local.cidrsubnet_public
  name                = local.vpc_name

  azs = local.azs

  # For every value of numbers of AZ, join the AZ name with subnet name
  public_subnet_names      = [for value in local.azs : join("-", [value, local.public_subnet_name])]
  private_subnet_names     = [for value in local.azs : join("-", [value, local.private_subnet_workload_name])]
  database_subnet_names    = [for value in local.azs : join("-", [value, local.private_subnet_datatier_name])]
  elasticache_subnet_names = [for value in local.azs : join("-", [value, local.private_subnet_tgw_name])]
}

locals {
  partition         = cidrsubnets(data.aws_vpc_ipam_preview_next_cidr.previewed_cidr.cidr, 1, 2, 3, 3) # result = 3 Sub CIDRs with prefixes 25, 26, 27, 27
  cidrsubnet_public = cidrsubnets(local.partition[2], 1, 1)                                            # Result = 1 Sub CIDR with prefix 28
  cidrsubnet_wld    = cidrsubnets(local.partition[0], 1, 1)                                            # Result = 1 Sub CIDR with prefix 26
  cidrsubnet_data   = cidrsubnets(local.partition[1], 1, 1)                                            # Result = 1 Sub CIDR with prefix 27
  cidrsubnet_tgw    = cidrsubnets(local.partition[3], 1, 1)                                            # Result = 1 Sub CIDR with prefix 28
  azs               = formatlist("${data.aws_region.current.name}%s", ["a", "b"])
}

# Reusable local variables for VPC module
locals {
  vpc_name           = "xxxxxx"
  public_subnet_name = "public_subnet"
}

# List of multiple private subnet names
locals {
  private_subnet_workload_name = "workload_subnet"
  private_subnet_datatier_name = "datatier_subnet"
  private_subnet_tgw_name      = "transit_gateway_subnet"
}

what is the issue here? Thank you in advance.