Terraform AWS Network Templates

public_private_subnets_ipv4_only

locals {
  main_vpc_cidr_block = "10.0.0.0/16"
  public_subnets = {
    "PublicSubnetA" = {
      cidr_block           = "10.0.1.0/24",
      availability_zone_id = "use1-az4"
    },
    "PublicSubnetB" = {
      cidr_block           = "10.0.2.0/24",
      availability_zone_id = "use1-az6"
    },
  }
  private_subnets = {
    "PrivateSubnetA" = {
      cidr_block           = "10.0.255.0/24",
      availability_zone_id = "use1-az4"
    },
    "PrivateSubnetB" = {
      cidr_block           = "10.0.254.0/24",
      availability_zone_id = "use1-az6"
    },
  }
}

## Main VPC
resource "aws_vpc" "main" {
  cidr_block           = local.main_vpc_cidr_block
  enable_dns_support   = true
  enable_dns_hostnames = true

  tags = merge(var.tags, {
    Name = "Main VPC"
  })
}

## Internet gateway for the main VPC
resource "aws_internet_gateway" "main" {
  vpc_id = aws_vpc.main.id

  tags = merge(var.tags, {
    Name = "Main Internet Gateway"
  })
}

## Public subnets
resource "aws_subnet" "public" {
  for_each = local.public_subnets

  vpc_id                  = aws_vpc.main.id
  availability_zone_id    = each.value.availability_zone_id
  cidr_block              = each.value.cidr_block
  map_public_ip_on_launch = true

  tags = merge(var.tags, {
    Name = each.key
  })
}

## Private subnets
resource "aws_subnet" "private" {
  for_each = local.private_subnets

  vpc_id                  = aws_vpc.main.id
  availability_zone_id    = each.value.availability_zone_id
  cidr_block              = each.value.cidr_block
  map_public_ip_on_launch = false

  tags = merge(var.tags, {
    Name = each.key
  })
}

## Public NAT gateway elastic ip
resource "aws_eip" "natgw" {
  vpc = true

  tags = merge(var.tags, {
    Name = "ElasticIP for NAT gateway"
  })
}

## Public NAT Gateway
resource "aws_nat_gateway" "main" {
  allocation_id = aws_eip.natgw.id
  subnet_id     = aws_subnet.public["PublicSubnetA"].id

  tags = merge(var.tags, {
    Name = "Public NAT GW"
  })

  # To ensure proper ordering, it is recommended to add an explicit dependency
  # on the Internet Gateway for the VPC.
  depends_on = [aws_internet_gateway.main]
}


## Route table for public subnets
resource "aws_route_table" "public" {
  vpc_id = aws_vpc.main.id

  route {
    cidr_block = "0.0.0.0/0"
    gateway_id = aws_internet_gateway.main.id
  }

  tags = merge(var.tags, {
    Name = "Public Subnets route table"
  })
}

## Route table for private subnets
resource "aws_route_table" "private" {
  vpc_id = aws_vpc.main.id

  route {
    cidr_block = "0.0.0.0/0"
    gateway_id = aws_nat_gateway.main.id
  }

  tags = merge(var.tags, {
    Name = "Private Subnets route table"
  })
}

## Main route table association
resource "aws_main_route_table_association" "main" {
  vpc_id         = aws_vpc.main.id
  route_table_id = aws_route_table.private.id
}

## Route table association for public subnets
resource "aws_route_table_association" "public" {
  for_each = local.public_subnets

  subnet_id      = aws_subnet.public["${each.key}"].id
  route_table_id = aws_route_table.public.id
}

public_private_subnets_ipv6_support.tf

locals {
  main_vpc_cidr_block = "10.0.0.0/16"
  public_subnets = {
    "PublicSubnetA" = {
      cidr_block           = "10.0.1.0/24",
      availability_zone_id = "use1-az4"
    },
    "PublicSubnetB" = {
      cidr_block           = "10.0.2.0/24",
      availability_zone_id = "use1-az6"
    },
  }
  private_subnets = {
    "PrivateSubnetA" = {
      cidr_block           = "10.0.255.0/24",
      availability_zone_id = "use1-az4"
    },
    "PrivateSubnetB" = {
      cidr_block           = "10.0.254.0/24",
      availability_zone_id = "use1-az6"
    },
  }
}

## Main VPC
resource "aws_vpc" "main" {
  cidr_block           = local.main_vpc_cidr_block
  enable_dns_support   = true
  enable_dns_hostnames = true

  assign_generated_ipv6_cidr_block = true

  tags = merge(var.tags, {
    Name = "Main VPC"
  })
}

## Internet gateway for the main VPC
resource "aws_internet_gateway" "main" {
  vpc_id = aws_vpc.main.id

  tags = merge(var.tags, {
    Name = "Main Internet Gateway"
  })
}

## Egress-only Internet gateway for the main VPC [IPv6 only]
resource "aws_egress_only_internet_gateway" "main" {
  vpc_id = aws_vpc.main.id

  tags = merge(var.tags, {
    Name = "Main Egress-only Internet Gateway"
  })
}

## Public subnets
resource "aws_subnet" "public" {
  for_each = local.public_subnets

  vpc_id                  = aws_vpc.main.id
  availability_zone_id    = each.value.availability_zone_id
  cidr_block              = each.value.cidr_block
  map_public_ip_on_launch = true

  tags = merge(var.tags, {
    Name = each.key
  })
}

## Private subnets
resource "aws_subnet" "private" {
  for_each = local.private_subnets

  vpc_id                  = aws_vpc.main.id
  availability_zone_id    = each.value.availability_zone_id
  cidr_block              = each.value.cidr_block
  map_public_ip_on_launch = false

  tags = merge(var.tags, {
    Name = each.key
  })
}

## Public NAT gateway elastic ip
resource "aws_eip" "natgw" {
  vpc = true

  tags = merge(var.tags, {
    Name = "ElasticIP for NAT gateway"
  })
}

## Public NAT Gateway
resource "aws_nat_gateway" "main" {
  allocation_id = aws_eip.natgw.id
  subnet_id     = aws_subnet.public["PublicSubnetA"].id

  tags = merge(var.tags, {
    Name = "Public NAT GW"
  })

  # To ensure proper ordering, it is recommended to add an explicit dependency
  # on the Internet Gateway for the VPC.
  depends_on = [aws_internet_gateway.main]
}


## Route table for public subnets
resource "aws_route_table" "public" {
  vpc_id = aws_vpc.main.id

  route {
    cidr_block = "0.0.0.0/0"
    gateway_id = aws_internet_gateway.main.id
  }

  route {
    ipv6_cidr_block        = "::/0"
    egress_only_gateway_id = aws_egress_only_internet_gateway.main.id
  }

  tags = merge(var.tags, {
    Name = "Public Subnets route table"
  })
}

## Route table for private subnets
resource "aws_route_table" "private" {
  vpc_id = aws_vpc.main.id

  route {
    cidr_block = "0.0.0.0/0"
    gateway_id = aws_nat_gateway.main.id
  }

  route {
    ipv6_cidr_block        = "::/0"
    egress_only_gateway_id = aws_egress_only_internet_gateway.main.id
  }

  tags = merge(var.tags, {
    Name = "Private Subnets route table"
  })
}

## Main route table association
resource "aws_main_route_table_association" "main" {
  vpc_id         = aws_vpc.main.id
  route_table_id = aws_route_table.private.id
}

## Route table association for public subnets
resource "aws_route_table_association" "public" {
  for_each = local.public_subnets

  subnet_id      = aws_subnet.public["${each.key}"].id
  route_table_id = aws_route_table.public.id
}