DNS
used to convert human-friendly domain names into an IP address
IPv4
- older
- are running out
- 32-bit friendly
- only has 4 billion addresses
IPv6
- created to solve the depletion issue with IPv4
- 128 bits
- 340 undecillion addresses
- eventually we’ll all need to migrate to IPv6
Top-Level Domain
last word of a domain name
- controlled by IANA
Second Level Domain
the second-to-last word in a domain name
Domain Registrar
an authority that can assign domains under top-level domain names and register them with InterNIC
Examples of Top-Level Domains
.com .gov .edu .org, etc.
InterNIC
a service of ICANN which enforces uniqueness of domain names
DNS Record Type: SOA Record
supplies:
- name of server that supplied data for that zone
- administrator of the zone
- current version of the data file
- default # of seconds for the Time-To-Live on resource records
DNS Record Type: NS Record
used by top-level domain servers to direct traffic to the content DNS server that contains the authoritative DNS records
DNS Record Type: A Record
Address Record
- fundamental type of DNS record
- used by a computer to translate the name of a domain to an IP address
- most common kind of DNS record
ex: translates http://www.acloud.guru to http://123.10.10.80
Time to Live (TTL)
- how long the DNS record gets caches
- the lower the TTL the faster the changes propagate across the internet
- important to reduce TTLs before making a big change or migration
DNS Record Type: CNAME
- canonical name
- used to resolve one domain name to another
ex: www.example.com points to example.com
AWS Alias Records
- used to map resources record sets in your hosted zone to load balancers, CloudFront distributions or S3 buckets
ex: map www.example.com to elb124.elb.amazonaws.com
- used to map resources record sets in your hosted zone to load balancers, CloudFront distributions or S3 buckets
Naked Domain Names
a. k.a. Zone Apex Records
- just the domain name without a subdomain
ex: http://acloudguru.com
- CNAMES cannot be used on Naked domain names, but an A Record/Alias can
7 routing policies available on Route 53
1) simple routing
2) weighted routing
3) latency-based routing
4) failover routing
5) geolocation routing
6) geoproximity routing (traffic flow only)
7) multi-value answer routing
Where do you create routing policies?
Route 53 -> Hosted Zones -> Create new record
Route 53 Exam tips
- understand difference between a CNAME and an Alias record
- given the choice for CNAME or Alias record, always choose the Alias record
- understand DNS record types: SOA, CNAME, NS, A
Route 53 Simple Routing Policy*
one record goes to multiple IP addresses
when user request the site, they are given an IP at random
Route 53 Failover Routing Policy
used when you want an active/passive setup*
eg. you have a primary site in one AZ and a secondary DR site in another AZ
- route 53 monitors the health of your endpoints with a health check*
- route 53 will failover to the secondary when necessary
Route 53 Geolocation Routing Policy
lets you choose where your traffic will be sent based on the geographic location of your end users *
- can be country or continent
- use cases:
- – localization for different countries
- country-based regulations
Route 53 Traffic Flow
uses a combination of geographic location, latency, availability to route traffic
Route 53 Geoproximity Routing
- requires Traffic Flow*
- lets Route 53 route traffic to resources based on the geographic location of your users and your resources
- optionally can choose to route more or less traffic to a given resource using a bias
- very complex, probably not on exam
bias
expands or shrink the size of a geographic region
