DNS record types

Question

I am going to write here everything about DNS record types to help understand it myself and others.

Pleasure is mine, if you will write what you know about this topic.

It is not about programming, but it is important to find Your web pages on Internet.
Do not public Your true records, only examples to understand the problematics :-)

Answer 1

Thank you for useful info!👍😊✨ Bookmarked😊

Answer 2

According to RFC 1035 we have 16 following type values:

A = a host Address
NS = an authoritative Name Server
MD = a Mail Destination (Obsolete - use MX)
MF = a Mail Forwarder (Obsolete - use MX)
CNAME = the Canonical NAME for an alias
SOA = marks the Start Of a zone of Authority
MB = a MailBox domain name (EXPERIMENTAL)
MG = a Mail Group member (EXPERIMENTAL)
MR = a Mail Rename domain name (EXPERIMENTAL)
NULL = a NULL RR (EXPERIMENTAL)
WKS = a Well Known Service description
PTR = a domain name PoinTeR
HINFO = Host INFOrmation
MINFO = Mailbox or mail list INFOrmation
MX = Mail eXchange
TXT = TeXT strings

Answer 3

Let us start with MX records according to RFC 974 (January 1986):

RFC 974 MAIL ROUTING AND THE DOMAIN SYSTEM part 1:

This RFC presents a description of how mail systems on the Internet
are expected to route messages based on information from the domain
system described in RFCs 882, 883 and 973. Distribution of this memo
is unlimited.

Introduction

The purpose of this memo is to explain how mailers are to decide how
to route a message addressed to a given Internet domain name. This
involves a discussion of how mailers interpret MX RRs, which are used
for message routing. Note that this memo makes no statement about
how mailers are to deal with MB and MG RRs, which are used for
interpreting mailbox names.

Under RFC-882 and RFC-883 certain assumptions about mail addresses
have been changed. Up to now, one could usually assume that if a
message was addressed to a mailbox, for example, at LOKI.BBN.COM,
that one could just open an SMTP connection to LOKI.BBN.COM and pass
the message along. This system broke down in certain situations,
such as for certain UUCP and CSNET hosts which were not directly
attached to the Internet, but these hosts could be handled as special
cases in configuration files (for example, most mailers were set up
to automatically forward mail addressed to a CSNET host to
CSNET-RELAY.ARPA).

Under domains, one cannot simply open a connection to LOKI.BBN.COM,
but must instead ask the domain system where messages to LOKI.BBN.COM
are to be delivered. And the domain system may direct a mailer to
deliver messages to an entirely different host, such as SH.CS.NET.
Or, in a more complicated case, the mailer may learn that it has a
choice of routes to LOKI.BBN.COM. This memo is essentially a set of
guidelines on how mailers should behave in this more complex world.

Readers are expected to be familiar with RFCs 882, 883, and the
updates to them (e.g., RFC-973).

Answer 4

RFC 974 MAIL ROUTING AND THE DOMAIN SYSTEM part 2:

What the Domain Servers Know

The domain servers store information as a series of resource records
(RRs), each of which contains a particular piece of information about
a given domain name (which is usually, but not always, a host). The
simplest way to think of a RR is as a typed pair of datum, a domain
name matched with relevant data, and stored with some additional type
information to help systems determine when the RR is relevant. For
the purposes of message routing, the system stores RRs known as MX
RRs. Each MX matches a domain name with two pieces of data, a
preference value (an unsigned 16-bit integer), and the name of a
host. The preference number is used to indicate in what order the
mailer should attempt deliver to the MX hosts, with the lowest
numbered MX being the one to try first. Multiple MXs with the same
preference are permitted and have the same priority.

In addition to mail information, the servers store certain other
types of RR's which mailers may encounter or choose to use. These
are: the canonical name (CNAME) RR, which simply states that the
domain name queried for is actually an alias for another domain name,
which is the proper, or canonical, name; and the Well Known Service
(WKS) RR, which stores information about network services (such as
SMTP) a given domain name supports.

Answer 5

Examples of MX Records:

MX XX server.domain.tld

wikipedia.org MX preference = 10, mail exchanger = mchenry.wikimedia.org
wikipedia.org MX preference = 50, mail exchanger = lists.wikimedia.org

wikipedia.org
MX 10 mx1001.wikimedia.org
MX 50 mx2001.wikimedia.orr

w3schools.com
MX 10 aspmx.l.google.com
MX 20 alt1.aspmx.l.google.com
MX 20 alt2.aspmx.l.google.com
MX 30 aspmx5.googlemail.com
MX 30 aspmx3.googlemail.com
MX 30 aspmx4.googlemail.com
MX 30 aspmx2.googlemail.com

10, 20, 30,... are priorities "The preference number is used to indicate in what order the mailer should attempt deliver to the MX hosts, with the lowest numbered MX being the one to try first."

Answer 6

Let's start from ABC.... good luck. I wish some people will gather here