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DNS

DNS Records
nslookup/dig
Record
Description
Resource Record
A domain name, usually a fully qualified domain name, is the first part of a Resource Record. If you don't use a fully qualified domain name, the zone's name where the record is located will be appended to the end of the name.
TTL
In seconds, the Time-To-Live (TTL) defaults to the minimum value specified in the SOA record.
Record Class
Internet, Hesiod, or Chaos
Start Of Authority (SOA)
It should be first in a zone file because it indicates the start of a zone. Each zone can only have one SOA record, and additionally, it contains the zone's values, such as a serial number and multiple expiration timeouts.
Name Servers (NS)
The distributed database is bound together by NS Records. They are in charge of a zone's authoritative name server and the authority for a child zone to a name server.
IPv4 Addresses (A)
The A record is only a mapping between a hostname and an IP address. 'Forward' zones are those with A records.
Pointer (PTR)
The PTR record is a mapping between an IP address and a hostname. 'Reverse' zones are those that have PTR records.
Canonical Name (CNAME)
An alias hostname is mapped to an A record hostname using the CNAME record.
Mail Exchange (MX)
The MX record identifies a host that will accept emails for a specific host. A priority value has been assigned to the specified host. Multiple MX records can exist on the same host, and a prioritized list is made consisting of the records for a specific host.
Command
Description
nslookup $TARGET
Identify the A record for the target domain.
nslookup -query=A $TARGET
Identify the A record for the target domain.
dig $TARGET @<nameserver/IP>
Identify the A record for the target domain.
dig a $TARGET @<nameserver/IP>
Identify the A record for the target domain.
nslookup -query=PTR <IP>
Identify the PTR record for the target IP address.
dig -x <IP> @<nameserver/IP>
Identify the PTR record for the target IP address.
nslookup -query=ANY $TARGET
Identify ANY records for the target domain.
dig any $TARGET @<nameserver/IP>
Identify ANY records for the target domain.
nslookup -query=TXT $TARGET
Identify the TXT records for the target domain.
dig txt $TARGET @<nameserver/IP>
Identify the TXT records for the target domain.
nslookup -query=MX $TARGET
Identify the MX records for the target domain.
dig mx $TARGET @<nameserver/IP>
Identify the MX records for the target domain.