# AWS Route53, VPC, and HA Notes

Hello Readers,

This is part 4 of the 5-part Series on cracking the AWS Solutions Architect - Associate Exam. In this section, We will be covering notes on the topics: Route53(DNS), VPC(Virtual Private Cloud), and High-Availability.

[Click here](https://blog.hellokarthic.com/aws-db-notes)  for part 3 - AWS Databases.

I've divided the notes into a 5 part series.

- **Part 1:**  [Introduction and AWS S3](https://blog.hellokarthic.com/aws-saa-notes) 
- **Part 2:**  [AWS EC2](https://blog.hellokarthic.com/aws-ec2-notes) 
- **Part 3:**  [Databases](https://blog.hellokarthic.com/aws-db-notes) 
- **Part 4:**  [DNS, VPC, and HA(High-Availability)](https://blog.hellokarthic.com/aws-dns-vpc-ha-notes) 
- **Part 5:**  [Application Services and Serverless + Bonus](https://blog.hellokarthic.com/aws-applications-serverless-notes) 

### Route53 Notes
---

Domain-name -> NS -> SOA -> A/CNAME/Alias

- NS - name server. It tells which server: Awsdns/GoDaddy/Bigrock.
- SOA - Start of authority, gives information about the alias/A/CNAME
- A - Address, gives IP address
- CNAME - canonical name, points to another domain name
	- CNAME cannot be given for naked domain name (apex records) For Ex: the naked domain is google.com; instead, CNAME is for m.google.com
- Alias - points to a DNS ( Ex: ALB, CDN, S3 )
- MX - for mail exchange server
- PTR - the reverse of A record. Lookup Ip address for the domain name.

#### Types of DNS Routing
- Simple Routing
- Weighted Routing ( you can distribute traffic %; also add health checks)
- Latency-based Routing
- Failover Routing
- Geolocation Routing ( for specific location)
- GeoProximity Routing (Traffic flow only) (based on physical distance)
- Multivalue Answer Routing (Simple Routing + health checks)

### VPC Notes
---
- Disable Source/Destination checks from **NAT Instances** when configuring.
- **Direct connect** - Dedicated connection from local office datacenter to AWS datacenter.
- **Global Acceleration** - Let your users access your application via edge location (Superfast) increases availability and performance
	- You are assigned 2 static IP address/ Bring your own
	- You can attach ALB, NLB, or EC2 instance
- **VPC Endpoint** - lets you connect your VPC with selected AWS Services without the need for NAT gateway, Internet Gateway, etc. Two types:
	- Interface Endpoint - attached ENI to ec2
	- Gateway Endpoint - Connects with S3, DynamoDB

### HA Notes
---
Autoscaling has 3 components
- Groups - Logical component grouping
- Configuration Templates - Groups uses launch template/configuration
- Scaling Policies
	- **Target tracking scaling:** Applied to check the ASGAvgCPUUtilization
	- **Step Scaling:** Adjust the capacity based on step adjustment instead of the target
	- **Simple Scaling:** Changes the capacity based on a single adjustment
- Scaling Options - Configure conditions (CPU, memory, schedule, etc). There are 5 options. They are:
	- Maintain current instance levels at all times (ex: min 5 instances always)
	- Scale Manually
	- Scale based on a schedule
	- Scale based on a demand
	- Use predictive scaling

Continue reading  [Part 5 - AWS Application Services and Serverless Notes](https://blog.hellokarthic.com/aws-applications-serverless-notes) ...