# Amazon Route 53 (AWS Certified Solutions Architect - Associate) ## What is DNS? * DNS = Domain Name System * It translates human friendly hostnames into the machine IP address. ex: www.google.com => 172.17.18.36 * DNS is the backbone of the internet. * DNS uses hierarchical naming structure .com example.com www.example.com api.example.com ## DNS Terminologies * **Domain Registrar** * This is where you are going to register your domain names. * Amazon Route 53, GoDaddy, etc. * **DNS Records** * A, AAAA, CNAME, NS, etc. * **Zone File** * It contains all DNS records. * This is how to match these hostnames to IPs or addresses. * **Name Servers** * It resolves DNS queries (Authoritative or Non-Authoritative). * **Top Level Domain (TLD)** * amazon.com, google.com * ![](https://cdn.hashnode.com/res/hashnode/image/upload/v1720619678872/883c6774-bfd0-4f14-b4da-ae4e8e6fd2f0.png align="center") ## How DNS works? * Please refer [this](https://rgitsc.udemy.com/course/aws-certified-solutions-architect-associate-saa-c03/learn/lecture/28384280#overview) Udemy lecture. --- ## Amazon Route 53 * A highly available, scalable, fully managed and Authoritative DNS * Authoritative = the customer (you) can update the DNS records * Route 53 is also a Domain Registrar. * It has ability to check the health of your resources. * It is the only AWS service with 100% SLA. * 53 in Route 53 refers to the traditional DNS port. ### Route 53 - Records * How you want to route traffic for a domain. * Each record contains: * Domain/sub-domain name - ex: example.com * Record Type - ex: A, AAAA, etc. * Value - ex: 12.34.56.78 * Routing Policy - how Route 53 responds to queries * TTL (Time To Live) - amount of time the record cached at DNS Resolvers * Route 53 supports the following DNS record types: * (must know) A / AAAA / CNAM / NS * (advanced) CAA / DS / MX / NAPTR / PTR / SOA / TXT / SPF / SRV ### Route 53 - Record Types * A - maps a hostname to IPv4 * AAAA - maps a hostname to IPv6 * CNAME - maps a hostname to another hostname * The target is a domain name which must have A or AAAA record * Can't create a CNAME record for top node of a DNS namespace (Zone Apex) ex: you can't create for example.com, but can create for www.example.com * NS - Name Servers for the Hosted Zone * Control how traffic is routed for a domain ### Route 53 - Hosted Zones * A container for records that define how to route traffic to a domain and sub-domains. * There are 2 types of Hosted Zones: * Public Hosted Zones - contains records that specify how to route traffic on the internet (public domain names) ex: application1.mypublicdomain.com * Private Hosted Zones - contains records that specify how you route traffic within one or more VPCs (private domain names) ex: application1.company.internal * You pay $0.50 per month per hosted zone. ### Route 53 - Records TTL * High TTL - ex: 24hr * Less traffic on Route 53 * Possibly outdated records * Low TTL - ex: 60sec * More traffic on Route 53 (more cost) * Records are outdated for less time * Easy to change records * Except for Alias records, TTL is mandatory for each DNS record ### CNAME vs Alias * AWS resource (Load Balancer, CloudFront, etc.) expose on AWS hostname: * lb1-1234.us-east-1.elb.amazonaws.com and we want myapp.mydomain.com * We have 2 options: * CNAME * Points a hostname to **any other hostname** (app.mydomain.com => xyz.anything.com) * Only for **non-root domain** (app.mydomain.com and not for mydomain.com) * Alias * Points a hostname to an **AWS resource** (app.mydomain.com => xyz.amazonaws.com) * Works for **root and non-root domain** (mydomain.com) * Free of charge * Native health check ### Route 53 - Alias Records * Maps a hostname to an AWS resource. * An extension to DNS functionality. * Automatically recognizes changes in the resource's IP addresses. * Unlike CNAME, it can be used for the top node of a DNS namespace (Zone Apex) ex: example.com * Alias Record is always of type A/AAAA for AWS resources (IPv4/IPv6). * You can't set the TTL. **Alias Records Targets** * Elastic Load Balancers * CloudFront Distributions * API Gateway * Elastic Beanstalk environments * S3 Websites * VPC Interface Endpoints * Global Accelerator * Route 53 record in the same hosted zone * Note: * **You can not set an ALIAS record for an EC2 DNS name** ## Route 53 - Routing Policy * Define how Route 53 responds to DNS queries. * Don't get confused by the word 'Routing'. * It is not the same as Load Balancer routing which routes the traffic. * DNS does not route any traffic, it only responds to the DNS queries. * Route 53 supports the following Routing Policies * Simple * Weighted * Failover * Latency based * Geolocation * Multi-Value Answer * Geoproximity (using Route 53 Traffic Flow feature) ### Routing Policy - Simple * Typically, route traffic to a single resource. * Can specify multiple values in the same record. * If multiple values are returned, a random one is chosen by the client. * When Alias enabled, specify only one AWS resource. * Can't be associated with Health Checks. ### Routing Policy - Weighted * Control the % of the requests that go to each specific resource. * Assign each record a relative weight: * traffic (%) = Weight for a specific record / Sum of all the weights for all records * Weights don't need to sum up to 100 * DNS records must have the same name and type. * Can be associated with Health Checks. * Use cases: load balancing between regions, testing new application versions, etc. * Assign a weight of 0 to a record to stop sending traffic to a resources. * If all records have weight of 0, then all records will be returned equally. ### Routing Policy - Latency based * Redirect to the resource that has the least latency close to us. * Super helpful when latency for users is a priority. * Latency is based on traffic between users and AWS regions. * Germany users may be directed to the US (if that's the lowest latency). * Can be associated with Health Checks ( has a Failover capability). ### Route 53 - Health Checks * HTTP Health Checks are only for **public resources.** * Health Check => Automated DNS Failover: * Health checks that monitor an endpoint (application, server, other AWS resource) * Health checks that monitor other health checks (Calculated Health Checks) * Health checks that monitor that monitor CloudWatch Alarms (full control) - ex: throttles of Dynamo DB, alarms on RDS, custom metrics, etc. (helpful for private resources) * Health Checks are integrated with CloudWatch Metrics. ### Health Checks - Monitor an Endpoint * About 15 global health checkers will check the endpoint health * Healthy/Unhealthy Threshold - 3 (default) * Interval - 30 sec (can set to 10 sec - higher cost) * if >18% of health checkers report the endpoint is healthy, Route 53 considers it **Healthy.** Otherwise it's **Unhealthy.** * Ability to choose which locations you want Route 53 to use. * Health Checks pass only when the endpoint responds with the **2xx** and **3xx** status codes. * Health Checks can be setup to pass/fail based on the text in the first **5120 bytes** of the response. * Configure your router/firewall to allow incoming requests from Route 53 Health Checkers. ### Health Checks - Calculated Health Checks * Combine the results of multiple health checks into a single health check. * You can use **AND, OR** or **NOT.** * Can monitor up to 256 child health checks. * Specify how many of the health checks need to pass to make the parent pass. * Usage: performance maintenance to your website without causing all the health checks to fail. ### Health Checks - Private Hosted Zones * Route 53 health checkers are outside the VPC. * They **can't access private endpoints** (private VPC or on-premises resource) * You can create a CloudWatch Metric and associate a CloudWatch Alarm, then create a health check that checks the alarm itself. ### Routing Policy - Failover * Write it down from google (not there in video) ### Routing Policy - Geolocation * Different from Latency-based. * This routing is based on user location. * Specify location by Continent, Country or by US State (if there's overlapping, most precise location is selected). * Should create a **Default** record (in case there's no match on location). * Use cases: website localization, restrict content distribution, load balancing, etc.) * Can be associated with Health Checks. ### Routing Policy - Geoproximity * Route traffic to your resources based on the geographic location of users and resources. * Ability to **shift more traffic to resources** based on the defined **bias**. * To change the size of the geographic region, specify bias values: * To expand (1 to 99) - more traffic to the resource * To shrink (-1 to -99) - less traffic to the resource * Resources can be : * AWS resources (specify AWS region) * Non-AWS resources (specify Latitude and Longitude) * You must use Route 53 Traffic Flow (advanced) to use this feature ### Routing Policy - IP based * Routing is based on clients IP addresses. * You provide a list of CIDRs for your clients and the corresponding endpoints/locations (user-IP-to-endpoint mapping). * Use cases: Optimize performance, reduce network costs, etc. * Ex: route end users from a particular ISP to s specific endpoint. ### Routing Policy - Multi Value * Use when routing traffic to multiple resources. * Route 53 return multiple values/resources. * Can be associated with Health Checks (return only values for healthy resources). * Up to 8 healthy records are returned for each Multi-Value query. * **Multi-Value is not a substitute for having an ALB.** ## Domain Registrar VS DNS Service * You can buy or register your domain name with a Domain Registrar typically by paying annual charges (ex: GoDaddy, Amazon Registrar, etc.) * The Domain Registrar usually provides you with a DNS Service to manage your DNS Records. * But you can use another DNS service to manage your DNS records. * Ex: Purchase the domain from GoDaddy and use Route53 to manage your DNS records. ### 3rd Party Registrar with Amazon Route 53 * If you buy your domain on a 3rd party registrar, you can still use Route 53 as the DNS service provider. * Create a public hosted zone in Route 53. * Update NS records on 3rd party website to use Route 53 Name Servers. * **Domain Registrar != DNS Service** * But every Domain Registrar usually comes with some DNS features.