DNS record types

A

A, or address, records describe the IP that a given DNS node has.

MaraDNS optionally uses the 'A' to signify an A record. This has one data-dependent field: The ip for the node in question, in dotted decimal (e.g. 192.168.42.55) format.

MX

MX, or mail exchange, records describe the machines to contact in order to send mail to a given DNS node.

This has two data-dependent fields: The preference for the mail exchanger (lower preferences get higher priority), and the name of the DNS node to deliver mail to.

NS

A NS record tells name servers which machines are in charge of a given domain zone.

This has one data-dependent field: The name of the DNS node which a given NS record points to.

Any given zone must have one or more NS records. If no NS records are present in a zone, MaraDNS will synthesize NS records for the zone in question. If one wishes to set up their own NS records, all of the NS records for a given DNS zone need to be placed immediately after the SOA record.

MaraDNS also supports delegation NS records, which name the DNS servers for a sub-zone, which usually is on another DNS server. DNS allows for people to delegate sub-zones in DNS. Just as the "." server delegates any name that ends in ".com." to another set of name servers, and the ".com." name servers, in turn, delegate any names that ends in "example.com.", such as "www.example.com.", to the "example.com." name servers, the "example.com." name servers may further delegate sub-zones.

For example, if example.com wishes to sub-delegate "john.example.com." to John who works at Example, inc., lines like this can be added to the example.com zone file:

john.example.com. NS ns1.john.example.com.
john.example.com. NS ns2.john.example.com.
# It's important to provide "glue"; in other words, let the world know
# the IPs for these name servers.
ns1.john.example.com. 10.9.8.7
ns2.john.example.com. 10.5.77.65

John, who is running is own nameservers with the IPs 10.9.8.7 and 10.5.77.65 then has a zone file for john.example.com. that looks something like this:

# It is best if the NS records for a subzone agree with the delegation
# records above
john.example.com. NS ns1.john.example.com.
john.example.com. NS ns2.john.example.com.

ns1.john.example.com. 10.9.8.7
ns2.john.example.com. 10.5.77.65

# Now that that is out of the way, here is the rest of the zone
john.example.com. 10.9.8.7
www.john.example.com. 10.5.77.65
john.example.com. MX 10 mail.john.example.com.
mail.john.example.com. 10.9.8.7

SOA

This is a record used when using DNS to synchronize data between multiple computers. Details on how this record works is in the DNS master document.

A given zone must have precisely one SOA record. If a SOA record is not present in a zone file, MaraDNS will synthesize a SOA record. If the record is in a zone file, it must be the first line of the zone file. Any other use of a SOA record will result in MaraDNS returning an error.

TXT

TXT, or text, records are arbitrary text strings which can be attached to given DNS nodes. Certain protocols, such as SPF, use this field to store protocol-specific data.

This has one data-dependent field: The text string in question.