Route 53 Flashcards
what is DNS?
Domain Name System which translates the human friendly hostnames
into the machine IP addresses
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,
What is Route 53?
This is a highly available and highly scalable fully managed and authoritative Domain name service.
It is also a domain registrar
Rout 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., 123.456.789.123
• 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
What are the different rout 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 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
What is TTL?
TTL - time to live. High TTL e.g 24hr, thisnmeans less traffic on route 53, and records will be outdated. Low TTL e.g. 60 secs, means high traffic to route 53 and records are more up to date, this is costs more.
CNAM vs Alias
in aws we have resource names exposed e.g. load balancers, cloudfront etc. but we want to s et name e.g. myapp.mydomain.com we can use CNAME and Alias.
• 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
Simple Routing policy?
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
Weighted routing policy?
By allocating weight to each resource/record then the traffic % will be routed according to the weighting set
• 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 the weight of 0, then all records will
be returned equally.
Latency-based routing policy?
This is where we want to route to the lowest latency resource. Route 53 will assess the latency and route the users to the nearest low latency resource from their location.
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)
Health Checks?
Way to check the health of public rources.
Health Check => Automated DNS Failover:
1. Health checks that monitor an endpoint
(application, server, other AWS resource)
2. Health checks that monitor other health
checks (Calculated Health Checks)
3. 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
Geolocation policy?
Specify a specific location to be routed to:
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
Geoproximity policy?
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
Multi Value?
Multi Value Query is used for routing to multiple resources:
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 EL
