Route table and subnet association "aws_route_table_association"

Terraform Providers AWS
1

Hi guys,

I started a few days ago to play around with TF and I’m struggling with creating an association between 6 subnets and 3 route tables, maybe you can give me a hint:

Vars:

subnets = {
    "private-1a" = { 
        "cidr" = "<cidr>", 
        "az" = "eu-central-1a", 
        "nat_gw" = false,
        "tag" = "private" },
    "private-1b" = { 
        "cidr" = "<cidr>", 
        "az" = "eu-central-1b", 
        "nat_gw" = false,
        "tag" = "private" },
    "private-1c" = { 
        "cidr" = "<cidr>", 
        "az" = "eu-central-1c", 
        "nat_gw" = false,
        "tag" = "private" },
    "public-1a" = { 
        "cidr" = "<cidr>", 
        "az" = "eu-central-1a", 
        "nat_gw" = true,
        "tag" = "public" },
    "public-1b" = { 
        "cidr" = "<cidr>", 
        "az" = "eu-central-1b", 
        "nat_gw" = true,
        "tag" = "public" },
    "public-1c" = { 
        "cidr" = "<cidr>", 
        "az" = "eu-central-1c", 
        "nat_gw" = true,
        "tag" = "public" },
    "private-eks-1a" = { 
        "cidr" = "<cidr>", 
        "az" = "eu-central-1a", 
        "nat_gw" = false,
        "tag" = "private-eks" },
    "private-eks-1b" = { 
        "cidr" = "<cidr>", 
        "az" = "eu-central-1b", 
        "nat_gw" = false,
        "tag" = "private-eks" },
    "private-eks-1c" = { 
        "cidr" = "<cidr>", 
        "az" = "eu-central-1c", 
        "nat_gw" = false,
        "tag" = "private-eks" }     
}

Subnets snippet:

resource "aws_subnet" "subnets" {
  for_each              = var.subnets

  vpc_id                = aws_vpc.main.id
  cidr_block            = each.value["cidr"]
  availability_zone = each.value["az"]

  tags                  = { 
    Name                = each.key
    Type                = each.value["tag"]
    AZ                  = each.value["az"] }
}

Route table snippet

resource "aws_route_table" "private_rt" {
  for_each          = aws_nat_gateway.nat_gateways

  vpc_id            = aws_vpc.main.id
  
  tags              = { 
    Name = "Private-RT-${each.value.tags["AZ"]}" 
    AZ                  = "${each.value.tags["AZ"]}" }
}

NAT GW snippet

resource "aws_nat_gateway" "nat_gateways" {
  for_each            = { for private_key, private_value in var.subnets:
  private_key => private_value if private_value["nat_gw"] }

  subnet_id           = aws_subnet.subnets[each.key].id
  allocation_id       = aws_eip.nat_eips[each.key].id
  depends_on          = [aws_internet_gateway.igw]

  tags                = { 
    Name              = "NAT-GW-${each.key}" 
    AZ                = "${each.value.az}"
    }
}

Out of the 9 created subnets, I want to create a for_each “aws_route_table_association” only for my 6 private subnets which also need to be associated with each of my 3 private route tables, according to its corresponding AZ. So the Route Table in “eu-central-1a” to have associated the subnets from AZ “eu-central-1a” (private & private-eks) and so on.

Any hints are much appreciated, I got my neck stuck in this for a while now…

Cheers!

Lucian.