Routing Flashcards
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