Route 53
What is DNS?
• Domain Name System which translates the human friendly hostnames into the machine IP addresses
• www.google.com => 172.217.18.36
• DNS is the backbone of the Internet
• DNS uses hierarchical naming structure
.com
example.com
api.example.com
www.example.com
DNS Terminologies
• Domain Registrar: Amazon Route 53, GoDaddy, …
• DNS Records: A, AAAA, CNAME, NS, …
• Zone File: contains DNS records
• Name Server: resolves DNS queries (Authoritative or Non-Authoritative)
• Top Level Domain (TLD): .com, .us, .in, .gov, .org, …
• Second Level Domain (SLD): amazon.com, google.com,
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
• Ability to check the health of your resources
• The only AWS service which provides 100% availability SLA
• Why Route 53? 53 is a reference to the traditional DNS port
Route 53 – Records
• How you want to route traffic for a domain
• Each record contains:
• Domain/subdomain Name – e.g., example.com
• Record Type – e.g., A or AAAA
• Value – e.g., 12.34.56.78
• Routing Policy – how Route 53 responds to queries
• TTL – amount of time the record cached at DNS Resolvers
• Route 53 supports the following DNS record types:
• (must know) A / AAAA / CNAME / 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 targe t is a domain name which must have an A or AAAA record
• Can’t create a CNAME record for the top node of a DNS namespace (Zone Apex)
• Example: you can’t create for example.com, but you 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 its subdomains
• Public Hosted Zones – contains records that specify how to route traffic on the Internet (public domain names) application1.mypublicdomain.com
• Private Hosted Zones – contain records that specify how you route traffic within one or more VPCs (private domain names) application1.company.internal
• You pay $0.50 per month per hosted zone
Route 53 – Records TTL (Time To Live)
• High TTL – e.g., 24 hr
• Less traffic on Route 53
• Possibly outdated records
• Low TTL – e.g., 60 sec.
• More traffic on Route 53 ($$)
• 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 Resources (Load Balancer, CloudFront...) expose an AWS hostname:
• lb1-1234.us-east-2.elb.amazonaws.com and you want myapp.mydomain.com
• CNAME:
• Points a hostname to any other hostname. (app.mydomain.com => blabla.anything.com)
• ONLY FOR NON ROOT DOMAIN (aka. something.mydomain.com)
• Alias:
• Points a hostname to an AWS Resource (app.mydomain.com => blabla.amazonaws.com)
• Works for ROOT DOMAIN and NON ROOT DOMAIN (aka 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), e.g.: example.com
• Alias Record is always of type A/AAAA for AWS resources (IPv4 / IPv6)
• You can’t set the TTL
Route 53 – Alias Records Targets
• Elastic Load Balancers
• CloudFront Distributions
• API Gateway
• Elastic Beanstalk environments
• S3 Websites
• VPC Interface Endpoints
• Global Accelerator accelerator
• Route 53 record in the same hosted zone
• You cannot set an ALIAS record for an EC2 DNS name
Route 53 – Routing Policies
• Define how Route 53 responds to DNS queries
• Don’t get confused by the word “Routing”
• It’s 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 Policies – 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 Policies – Weighted
• Control the % of the requests that go to each specific resource
• Assign each record a relative weight:
• 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…
• Assign a weight of 0 to a record to stop sending traffic to a resource
• If all records have weight of 0, then all records will be returned equally
Routing Policies – 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 CloudWatch Alarms (full control !!) – e.g., throttles of DynamoDB, alarms on RDS, custom metrics, … (helpful for private resources)
• Health Checks are integrated with CW 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)
• Supported protocol: HTTP, HTTPS and TCP
• 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 you router/firewall to allow incoming requests from Route 53 Health Checkers
Route 53 – Calculated Health Checks
• Combine the results of multiple Health Checks into a single Health Check
• You can use OR, AND, 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: perform maintenance to your website without causing all 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
you create 2 record but with same name and if one instances is unhealth failover policiy send to secondary instances
Routing Policies – 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 selected)
• Should create a “Default” record (in case there’s no match on location)
• Use cases: website localization, restrict content distribution, load balancing, …
• Can be associated with Health Checks
Routing Policies – 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 to use this feature
Route 53 –Traffic flow
• Simplify the process of creating and maintaining records in large and complex configurations
• Visual editor to manage complex routing decision trees
• Configurations can be saved as Traffic Flow Policy
• Can be applied to different Route 53 Hosted Zones (different domain names)
• Supports versioning
Routing Policies – 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 ELB
Domain Registar vs. DNS Service
• You buy or register your domain name with a Domain Registrar typically by paying annual charges (e.g., GoDaddy, Amazon Registrar Inc., …)
• 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
• Example: purchase the domain from GoDaddy and use Route 53 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 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
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