DNS Interview Question

DNS Components
•  Domain Name Space and resource records
•  Name servers
•  Resolvers
Query Function Types
There are two types of queries issued: recursive and iterative.
Recursive queries received by a server forces that server to find the information
requested or post a message back to the querier that the information cannot be found.
Iterative queries allow the server to search for the information and pass back the best
information it knows about. This is the type that is used between servers. Clients used
the recursive query. This is shown in the slide.
Generally (but not always), a server-to-server query is iterative and a client-resolverto-server query is recursive.
Example DNS Database
Example DNS Database
•  Records in the database include:
•  A—host’s IP address
•  PTR—host’s domain name, host identified by its IP address
•  CNAME—host’s canonical name, host identified by an alias domain name
•  MX—host’s or domain’s mail exchanger
•  NS—host’s or domain’s name server(s)
•  SOA—Indicates authority for the domain
•  TXT—generic text record
•  SRV—service location record
•  RP—text name of the person responsible for the domain DNS
WHOIS Command
•  Enables you to get more information on domain names, networks, etc., on the
•  ://ds.internic.net/cgi-bin/whois.
•  “whois ascend.com” (without the quotes).

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