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DNS

DNS stands for Domain Name System.
The goal of DNS was to displace the HOSTS.TXT file.
The three main components of DNS are
The domain name space and resource records Namespaces organized in a tree fashion. Each namespace stores some data («resource records»).
Name servers They hold information about the tree for which they are the authority - and optionally(?) the (cached) information of a portion of the rest of the domain tree's structure.
Resolvers Programs that communicate with name servers to extract the information they store.

Zones

Zones are units into which authoritative information is organized.
Zones can be distributed to name servers which then provide the data on a redundant basis.

Entry types

A The IP address of the host.
AAAA The IPv6 address of the host.
CAA
CNAME Canonical name. The value of a CNAME record points to a domain, not to an IP address. For example used for www.abc.xyz pointing to abc.xyz (which then has an A record).
DS
HINFO Identifies the CPU and OS used by the host
MX The mail exchange for the host. An MX record cannot point to a CNAME record.
NS The authoritative name server for the domain. An NS record cannot point to a CNAME record.
PTR A pointer to another part in the domain namespace.
SRV
SOA Identifies the start of a zone of authority
TLSA
TXT

Top level domain arpa

IPv4: in-addr.arpa, IPv6: ip6.arpa

Well known DNS servers

Some well known DNS servers include:

See also

host, dig
/etc/resolv.conf
Perl module Net::DNS
2181 Clarifications to the DNS Specification

Links

dns.google
Check global DNS propagation

Index

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