vpc.tf

 resource "aws_vpc" "main" {                
   cidr_block       = var.main_vpc_cidr
   instance_tenancy = "default"
 }

 resource "aws_internet_gateway" "IGW" {   
    vpc_id =  aws_vpc.main.id
 }

 resource "aws_subnet" "publicsubnets" {
   vpc_id     =  aws_vpc.main.id
   cidr_block = "${var.public_subnets}"
 }

 resource "aws_subnet" "privatesubnets" {
   vpc_id     =  aws_vpc.main.id
   cidr_block = "${var.private_subnets}"
 }

 resource "aws_route_table" "PublicRT" {
    vpc_id =  aws_vpc.main.id
    route {
        cidr_block  = "0.0.0.0/0"
        gateway_id  = aws_internet_gateway.IGW.id
     }
 }

 resource "aws_route_table" "PrivateRT" {
   vpc_id = aws_vpc.main.id
   route {
        cidr_block     = "0.0.0.0/0"
        nat_gateway_id = aws_nat_gateway.NATgw.id
   }
 }

 resource "aws_route_table_association" "PublicRTassociation" {
    subnet_id      = aws_subnet.publicsubnets.id
    route_table_id = aws_route_table.PublicRT.id
 }

 resource "aws_route_table_association" "PrivateRTassociation" {
    subnet_id      = aws_subnet.privatesubnets.id
    route_table_id = aws_route_table.PrivateRT.id
 }

 resource "aws_eip" "nateIP" {
   vpc   = true
 }
 
 resource "aws_nat_gateway" "NATgw" {
   allocation_id = aws_eip.nateIP.id
   subnet_id     = aws_subnet.publicsubnets.id
 }