README

Purpose of this Module

Although one can find various terraform modules to provision AWS VPC. This module mainly concentrate on

• How to avoid providing cumbersome vpcid, subnet id when creating various AWS resources?
• Make AWS resources more readable when navigating in AWS console. This became more useful when your AWS account has lot of resources.
• Apply simple strategies for creating resources and improve security. e.g. enforce RDS in private subnet, compute resources like ECS, EKS in private subnet.This become very useful when this module used by novice developer.
• Attach predefined tags to AWS resources. These tags play major role in tracking resources for
  • Monitoring. tools like Datadog depends heavily on tags
  • Cost

Dependencies and Prerequisites

• Terraform version 0.12 and higher
• AWS account
• AWS CLI

Important Variables

variable name	is required	Default Value	Type	Notes
vpc_cidr_block	Y		String	Valid CIDR Range
public_subnet_cidr_list	N	empty list	list	Valid list of CIDR range inline with vpc_cidr_block
private_app_subnet_list	N	empty list	list	Valid list of CIDR range inline with vpc_cidr_block
private_db_subnet_list	N	empty list	list	Valid list of CIDR range inline with vpc_cidr_block
region	N	eu-west-1	string	Valid AWS Region
region_id	N	euw1	string	Region Identifier. for more information about this please refer following sections
az_list	N	eu-west-1a,eu-west-1b, eu-west-1c	list	Define Az in which subnet to be get created. Availability zone inline with region.it's count must be same as cidr ranges define for subnets.
vpc_seq_id	N	001	string	Define sequence for combination of regionId,cost_centre and environment. one can define any random string,but it is better if is sequential number
seq_id	N	001	string	usually some sequential number. in this case it should be same as vpc_seq_id
environment	N	dev	string	indicates name of our environment.it can be anything. Possible values dev,cit,sit,uat,pprod,prod,n. for more information refer following sections.
cost_centre	N	na	string	A part of an organization to which bill might be charged.e.g. finance/it/hr/wholesale/retail/investment etc...

for complete list of variables please refer variables.tf of this module.

region

• Indicates region in which VPC to be created.
• Possible values :- https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/Concepts.RegionsAndAvailabilityZones.html
• e.g. for Europe ireland :- eu-west-1

region_id

• short indicator for region
• it can be max 5 char.
• for eu-west-1 it is euw1
• for ap-southeast-1, singapore i.e. apse1
• please note these are indicator for ideal region_id. one can use its own standard if needed.

cost_centre

• It represents an entity which will own cost for resources created in this VPC .
• Any org can have multiple departments wfollowing cost centres. following values are indicative.one can use their own indicator,but one need to follow same throughout.
• all small case letters
• length 1 to 4 chars

Possible Cost Centres	value
admin	admn
infrastructure	infra
techsupport	tsup
hr	hr
it	it
legal	lgl
finance	fin
wholesale	whsl
retail	rtl
manufacturing	mfg
banking	bank
investment	inv
marketing	mkt

environment

• It represents the environment for which this VPC created for.
• length 1 to 3 chars
• all small case letters
• Possible values

Value	Important Note
dev	for Development environment
cit	specific to Component Integration Testing
sit	specific to System Integration Testing
uat	specific to User Acceptance Testing
pre	specific to Preprod environment
n	VPC which is not for production env
p	VPC for Production environment

Important Notes for Tags

This module add/override following tags to various resources created.

Tag Key	Variable	Notes
RegionId	region_id	Represent indicator for region in which resource present
Environment	environment	Represent Environment.
CostCentre	cost_centre	some predefined, unique identifier across org for identifying entity responsible for cost.
VPCSeqId	vpc_seq_id	Indicator for VPC
VersionId	version_id	it is less signficant,but if anyone want to track it is good idea
BuildDate	build_date	it is less signficant,but if someone wants to track date(predefine date format defined in your org) then it is good indicator for date on which this component/resource created/updated
AppRole		it is constant with value network for various resources created by this module.

This module responsible for creating

Subnets	Notes
Public Subnet	Ideal for running Load Balancers (Application, Classic, Network), API Gateway....
Private subnet for Computing	Ideal for running Compute resources like AWS lambda, ElasticBeanstalk, EC2, ECS, EKS......
Private subnet for Persistence layer	A place for running RDS, NoSQL, Elastic search ....

Gateways	Notes
Nat Gateway	Responsible for Instances(EC2/Containers etc) in private subnet to communicate with the Internet but the reverse is not true. Associate public/Elastic IP with each Nat Gateway
Internet Gateway	Provide a target in your VPC route tables for internet-routable traffic. Perform network address translation (NAT) for instances that have been assigned public IPv4 addresses
VPN Gateway	Enable the on-premises network to connect to this VPC

AWS Resource	Notes
Single VPC
Route and Route tables

Example

module "vpc" {
source="git::https://github.com/polganesh/terraform-aws-vpc.git"
vpc_cidr_block = "10.10.0.0/16"
public_subnet_cidr_list = ["10.10.1.0/24", "10.10.2.0/24", "10.10.3.0/24"]
private_app_subnet_list = ["10.10.4.0/24", "10.10.5.0/24", "10.10.6.0/24"]
private_db_subnet_list = ["10.10.7.0/24", "10.10.8.0/24", "10.10.9.0/24"]
region = "eu-central-1"
region_id = "euc1"
az_list = ["eu-central-1a", "eu-central-1b", "eu-central-1c"]
vpc_seq_id = "001"
seq_id = "001"
environment = "n"
cost_centre = "tech"
build_date = "30092019"
version_id = "001"
}

AWS Resources created by this script

VPC
VPC name format	vpc-{region-id}-{environment}-{cost_centre}-{vpc_seq_id}
Example	vpc-euc1-n-tech-001
Important Notes	helpful for anyone to identify this VPC created in eu-central-1, for non prod account, cost for any resources created in this VPC will be managed by tech business unit in organization, it is first VPC in this AWS account with remaining combination

Subnets
Subnet name format	sub-{region-id}-{environment}-{cost_centre}-vpc{vpc_seq_id}-{pub,privApp,privDb}-{az-indicator}-{seq_id}
Example for public subnets	sub-euc1-n-tech-vpc001-pub-1a-001
	sub-euc1-n-tech-vpc001-pub-1b-001
	sub-euc1-n-tech-vpc001-pub-1c-001
Example for private App subnets	sub-euc1-n-tech-vpc001-privApp-1a-001
	sub-euc1-n-tech-vpc001-privApp-1b-001
	sub-euc1-n-tech-vpc001-privApp-1c-001
Example for private Db subnets	sub-euc1-n-tech-vpc001-privDb-1a-001
	sub-euc1-n-tech-vpc001-privDb-1b-001
	sub-euc1-n-tech-vpc001-privDb-1c-001

Route Tables
Route table format	rtb-{region-id}-{environment}-{cost_centre}-vpc{vpc_seq_id}-{pub,privApp,privDb}-{az-indicator}-{seq_id}
Example for route tables	rtb-euc1-n-tech-vpc001-pub-1a-001
	rtb-euc1-n-tech-vpc001-pub-1b-001
	rtb-euc1-n-tech-vpc001-pub-1c-001
	rtb-euc1-n-tech-vpc001-privApp-1a-001
	rtb-euc1-n-tech-vpc001-privApp-1b-001
	rtb-euc1-n-tech-vpc001-privApp-1c-001
	rtb-euc1-n-tech-vpc001-privDb-1a-001
	rtb-euc1-n-tech-vpc001-privDb-1b-001
	rtb-euc1-n-tech-vpc001-privDb-1c-001

Nat Gateways
Nat Gateway format	ngw-{region-id}-{environment}-{cost_centre}-vpc{vpc_seq_id}-{az-indicator}-{seq_id}
	ngw-euc1-n-tech-vpc001-1a-001
	ngw-euc1-n-tech-vpc001-1b-001
	ngw-euc1-n-tech-vpc001-1c-001

VPN Gateway
VPN Gateway format	vpngw-{region-id}-{environment}-{cost_centre}-{seq_id}
	vpngw-euc1-n-tech-001

Internet Gateway
Internet Gateway format	igw-{region-id}-{environment}-{cost_centre}-{seq_id}
	igw-euc1-n-tech-001