DNS / Route 53 Flashcards
Why is it called Route 53?
Think Route 66, in that it goes aross everything (one side of the country to the other) DNS is on port 53
What does DNS stand for?
Domain Name System
What is DNS used for?
DNS is used to convert human-friendly domain names into IP addresses
What does IP stand for?
Internet Protocol
What does an IP address do?
IP addresses are used by computers to identify each other on the network
What is a Top Level Domain?
The part of a website that goes after the last “.” (e.g. .com, .edu, .gov)
What is a second level domain name?
The second-to-last work in a domain name (optional)
e.g. the “co” in .co.uk
What does IANA stand for?
Internet Assigned Numbers Authority
How are top level domain names controlled?
They are controlled by IANA in a root zone database, which is a database of all available top level domains.
What is the key purpose of domain registrars?
Ensuring that all names in a given domain are unique.
What does SOA stand for?
Start Of Authority Record
What info is contained in an SOA?
- The name of the server that supplied data for the zone
- Administrator of the zone
- Current version of the data file
- default # of seconds for the TTL file on resource records
What does NS stand for?
Name Server Records
What is the purpose of an NS Record?
They are used by Top Level Domain servers to direct traffic to the Content DNS server which contains the authoritative DNS records.
What does the “A” stand for in “A” Record?
Address
What does an “A” Record do?
The A record is used by the computer to translate the name of the domain to an IP address
In the context of DNS, why is TTL important?
- TTL is the length of time that a DNS record is cached on either the Resolving Server or the user’s own local PC.
- The lower the TTL, the faster changes to DNS records take to propogate throughout the internet.
What does CName stand for?
Canonical Name
What does a CName do?
A CNAME is used to resolve one domain name to another
(Imagine looking in the phone book for BATMAN -> See West, Adam)
What is an Alias Record?
Alias Records are used to map resource record sets in your hosted zone to Elastic Load Balancers, CloudFront Distributions, or S3 buckets that are configured as websites.
What is a naked domain name?
a DNS server name that doesn’t have the “www” or any other subdomains
What is a zone apex record?
A DNS name that doesn’t have “www” or any of the other subdomains
What is the key difference between an Alias Record and a CName?
While both are used to map a DNS name to another, CNames cannot be used for naked domain names
Do Elastic Load Balances have pre-defined IPv4 addresses?
No, you resolve to them using a DNS name
On the exam, given the choice between an Alias Record and a CName, which should you pick?
Alias Records (CNAMEs can’t handle zone apex records)
What does the MX stand for in MX Record?
Mail Exchanger
What does the PTR stand for in PTR Record?
Pointer
At a high level, what does a PTR Record do?
Maps an IP address to a domain/host name
(Think inverse of an A record)
Can you buy domain names directly from AWS?
Yes, but it can take up to 3 days to register depending on the circumstances.
What are the common DNS types?
- SOA Records
- NS Records
- A Records
- CNAMES
- MX Records
- PTR Records
What is the limit to the number of domain names you can manage using Route53?
default limit is 50 domain names, but this can be increased by contacting AWS Support
Can an Alias record point to AWS Resources that are hosted in other accounts?
Yes, by manually entering the ARN
There is a website hosted in AWS that might get a lot of traffic over the next few weeks. If the application experiences a natural disaster at this time, what should be done to reduce potential disruption to users?
Use Route53 to route requests to another instance in a different region
