Week 4 - Name Resolution Flashcards
What is DNS? What does it do?
Domain Name System
DNS is a global network service that translates a string of letters into an IP address for you
What’s a domain name?
Domain names are unique, easy-to-remember letter addresses that can be translated into an IP address by the DNS
What is name resolution?
The method of using DNS to look up an IP address associated with a domain name
What are 4 things that must be configured for a host to operate on a network?
- IP address
- DNS server
- Router/Gateway
- Subnet mask
What are the 5 primary types of DNS servers?
- Caching name server
- Recursive name server
- Root name server
- TLD name server
- Authoritative name server
What do the caching name servers do?
They store a local copy of recent DNS lookups
the time it’s stored is based on the data’s TTL
What is a TTL in DNS? Every ____ has one
TTL = time to live in seconds
Every domain name has one, and it tells the name server how long to hold onto the name lookup data
What do recursive name servers do?
Recursive name servers perform a full address resolution protocol
How many root name server authorities are there? How are they distributed?
There are 13 root name server authorities and they are distributed using Anycast
What is anycast?
Anycast is a technique used by the name servers to route traffic depending on factors like link health, congestion, and location
Describe the steps a local recursive server takes to perform a full address resolution:
- Computer contacts root name server
- Root name directs traffic to TLD server
- TLD responds again with a redirect to the authoritative name server
- Authoritative name server responds with actual IP address
Describe the 5 primary types of DNS servers
- Caching - stores a local copy of DNS lookups
- Recursive - full address resolution name lookup
- Root - provides the name lookup service
- TLD - provides the last part of a domain and redirects to authoritative
- Authoritative - the organization that runs the domain, provides the IP address
Why is the hierarchical DNS lookup process important?
A computer sends traffic to an IP blindly and the hierarchical DNS lookup process prevents malicious intervention/redirection of traffic
What port is reserved for DNS?
DNS uses Port 53
What’s the difference between a DNS resolver and a DNS server?
the DNS resolver performs the lookup and resends the request when needed and the DNS server listens for the request of data
What is an A record in name resolution?
A single A Record points to a single domain name to a certain IPv4 address
What is a DNS Round Robin in name resolution?
repeatedly cycles through a list of items 1 by 1 in order
How does DNS Round Robin balance traffic?
DNS Round Robin cycles the separate client’s connection to each A record available in order
What is a Quad A record?
Same function as an A record but returns an IPv6 address instead of an IPv4
What is the CNAME resource record?
It’s the canonical name for a domain name and redirects traffic to the canonical domain
What is the MX resource record and what does it do?
Mail Exchange resource record handles the resolving of email domains
An MX record stores a mail server’s IP.
What is the SRV in name resolution?
The service resource record directs traffic to a specific service using its port
What is TXT and what is it used for?
It stores any additional information
What is ICANN? What do they do?
ICANN is the Internet Corporation for Assigned Names and Numbers
They distribute TLDs
What are the 3 parts of a domain?
- TLD .com, .org, .net
- domain google, youtube, twitch
- subdomain www.
What do you call all parts of a domain combined?
FQDN
Fully qualified domain name
What is a registrar?
a registrar is a company that works in accordance with ICANN to sell unregistered domain names
What’s the purpose of DNS zones?
DNS zones allow easier control over multiple levels of a domain
What are zone files? What 2 files does it contain?
Zone files declare all resource records for a zone and contain:
- SOA files (start of authority)
- NS files
What is SOA? Where do you find this?
Start of Authority
they are in zone files and indicate the zone and which name server is authoritative of it
What are NS records? Where are they found?
names other servers that might be in charge of the zone
they are found in zone files
What do reverse lookup zone files do?
Reverse lookup zone files let DNS resolvers ask for an IP and also provide the FQDN associated
What is a PTR?
pointer record
resolve an IP address to a name
