DNS 2 Flashcards
Learn about what DNS is and how it works
What are the characters in DNS
- Browser
- Function
- Resolver
- Authoritative name-servers
When your browser makes a DNS query what does it ask?
It asks a resolver.
What gets updated whenever you update a domain’s DNS records?
When you update a domain’s DNS records you update the authoritative name-server.
How does a resolver handle queries?
- The resolver checks its cache
- If that fails it finds the right authoritative name-server and asks it.
How does an authoritative name-server handle queries?
It checks its database for a match.
What are some other names for resolvers?
Other names for resolvers include:
- recursive resolver
- DNS recursor
- public DBS server
- recursive nameserver
- DNS resolution service
- caching-only nameserver
What are the two types of authoritative nameservers?
The two types of authoritative nameservers are:
- root nameserver
- TLD nameserver
What are the 3 levels of authoritative nameservers?
The three levels of authoritative nameservers are:
- root
- TLD
- Authoritative
What does the root nameserver?
The root nameserver provides the information required to locate the correct TLD nameserver.
What does the TLD nameserver do?
The TLD nameserver manages domains that share a common top level domain extension. hey act as a bridge between the root servers and the authoritative nameservers for specific domains, they direct DNS queries to the correct authoritative nameservers.
What does the authoritative nameserver do?
Authoritative nameservers provide answers to DNS queries such as a websites IP address.
What is the lifecycle of a DNS query?
- The user enters a url into the browser.
- The browser checks if it has an ip address for the website cached, if it doesn’t it asks a resolver.
- The resolver checks its cache to see if it has the ip address, if it doesn’t it asks the root nameserver
- The root nameserver gives the resolver the address of the TLD nameserver.
- The resolver asks the TLD nameserver and the TLD nameserver gives the resolver the address of the authoritative nameserver.
- The resolver asks the authoritative nameserver and the authoritative nameserver tells the resolver.
- The resolver tells the browser.
What are the 5 parts of a DNS record?
The 5 parts of a DNS record are:
- name
- type
- value
- class
- TTL
What is TTL?
TTL is time to live, it is how long the record will be cached for in seconds.
What does the class field specify?
The class field specifies the type of network the record applies to.
What does the type field specify?
The type field specifies what kind of data is associated with a domain or a host name.
What are the two types of DNS records the root nameserver can return?
The root nameserver can return NS records in the authority section and glue records in the additional section.
What does a NS record give you?
NS records give you the domain name of the server to communicate with next but not its IP address.
What does a glue record do?
A glue record provides the IP address for a domains authoritative nameserver when those nameservers are located within the same domain.
How many levels of subdomains are allowed?
Maximum 127.
How can you create a subdomain?
You can create a subdomain by creating a DNS record in your authoritative nameservers.
What are the 2 ways a nameserver can handle subdomains?
- Storing the DNS records itself
- Redirecting to another authoritative nameserver.
How do you avoid negative caching?
Negative caching can be avoided by making sure you don’t visit your domain before you create its DNS record.
What is negative caching?
Negative caching is storing information about unsuccessful DNS lookups in a cache.
