Global DNS (Route 53) Fundamentals

Question 1

What are the steps required for registering a DNS Domain?

Answer 1

o 1) Check the domain is available
o 2) Purchase the domain via a registrar (Route 53 can do this for you)
o 3) Hosting the domain (Route 53 allows you to register a domain and host it, or just host it, or just register it)
o 4) Records in the zone file (On the Name Servers that are authoritative / host the domain, you need to add records into the zone file – www, mail, ftp, etc. This completes the chain, and these are accessible from the internet)

Question 2

What is a Hosted Zone (or Zone)?

Answer 2

o A Zone or Hosted Zone is a container for DNS records relating to a particular domain (e.g. linuxacademy.com). Route 53 supports public hosted zones, which influence the domain that is visible from the internet and VPCs. Private hosted zones are similar, but only accessible from the VPC they are associated with

Question 3

What is a Public Zone?

Answer 3

 A public hosted zone is created when you register a domain with Route 53, when you transfer one to Route 53 or if you create one manually
 A hosted zone has the same name as the domain it relates to (e.g. linuxacademy.com will have a HZ called linuxacademy.com)
 A public zone is accessible either from internet-based DNS clients (e.g. your laptop) or from within any AWS VPC
 A hosted zone will have ‘name servers’ – these are the IP addresses you can give to a domain operator, so Route 53 becomes authoritative for that domain

Question 4

What is a Private Zone?

Answer 4

 Private Zones are created manually and associated with one or more VPCs – they are only accessible from those VPCs
 Private zones need enableDnsHostNames and enableDnsSupport enabled on a VPC
 Not all Route 53 features are supported (e.g. limitations on health checks)
 Split-View DNS is supported, enabling the same zone name for public and private zones – providing VPC resources with different records (e.g. testing, internal versions of websites)
 With split view, private is preferred – if no matches, public is used

Question 5

What are the key Record Set Types?

Answer 5

o DNS support different types of records, each providing different functionality. The key ones are the following:
o A Record (and AAAA): for a given host (www), an A record provides an IPv4 address (e.g. 10.0.0.1) and an AAAA provides an IPv6 address
o CNAME Record: Allows aliases to be created (not the same as an alias record). A machine such as allthethings.linuxacademy.com might have CNAMES for www, ftp and images. CNAMES cannot be used at the APEX of a domain (e.g. linuxacademy.com)
o MX Record: Provides the mail server for a given domain. Each MX record has a priority
o NS Record: Used to set the authoritative servers for a subdomain. .com would have NS servers for linuxacademy.com
o TXT Record: Used for descriptive text in a domain, often used to verify domain ownership
o Alias Record: An extension of CNAME, which can be used like an A record, with the functionality of a CNAME and none of its limitations. AWS does not charge for queries of alias records against AWS resources

Question 6

What are Health Checks?

Answer 6

o Health Checks can be created within Route 53, and are used to influence Route 53 routing decisions. 3 types:
o 1) Monitor the health of an endpoint (e.g. IP address or hostname)
o 2) Monitor the health of another health check (known as calculated health checks)
o 3) Monitor CloudWatch alarms – you may want to consider something unhealthy if your DynamoDB table is experiencing performance issues
o Route 53 Health Checkers: Global health check system that checks an endpoint in an agreed way, with an agreed frequency. >18% of checks report healthy => healthy, otherwise unhealthy
o HTTP / HTTPS pages can be health checked either every 10 or 30 seconds