DNS Record Types

One of the many challenges that we may face while attempting to make modifications to a zone file, is knowing what the different records are used for.  This article highlight several of the commonly used records in an attempt to help demystify them.

First, let's start with a look at a typical zone file.

;Panel 11.24.4-CURRENT_33868
; Zone file for liquidweb.com
$TTL 14400
@      86400    IN      SOA     ns.liquidweb.com. admin.liquidweb.com. (
2009022402      ; serial, todays date+todays
86400           ; refresh, seconds
7200            ; retry, seconds
3600000         ; expire, seconds
86400 )         ; minimum, seconds
 
liquidweb.com. 86400 IN NS   ns.liquidweb.com.
liquidweb.com. 86400 IN NS   ns1.liquidweb.com.
 
liquidweb.com.  IN A   209.59.139.21
 
localhost  IN A   127.0.0.1
 
liquidweb.com.  IN MX 0   liquidweb.com.
 
mail  IN CNAME  liquidweb.com.
www  IN CNAME   liquidweb.com.
ftp  IN A   209.59.139.21
cpanel  IN A   209.59.139.21
 
webmail  IN A   209.59.139.21
 
liquidweb.com.  IN    TXT    "v=spf1 a:email.liquidweb.com a:mxgate-02.liquidweb.com a:agile.liquidweb.com a:swift.liquidweb.com mx:liquidweb.com ~all"

TTL

Time to Live — The time to live value sets how long this information will be good for when a recursive DNS server queries for information on your domain name.  The value is typically set in seconds.

SOA

State of Authority — The state of authority record specifies the DNS server providing authoritative information about an Internet domain, the email of the domain administrator, the domain serial number, and several timers relating to refreshing the zone.

NS

Nameserver — The servers listed in the NS record are the authoritative nameservers for the domain.

MX

Mail Exchange record  — The MX record states the location that mail directed at  the domain will be sent.  MX records should always be fully qualified domain names, never just an IP address.

A

Address record — The address record assigns an IP address to a domain or subdomain name.  An A record will always be an IP address.

CNAME

Canonical name — The CNAME record makes one domain name an alias of another. The aliased domain gets all the subdomains and DNS records of the original. To put this in simple terms, a CNAME redirects requests to another record.  A CNAME record will always be a fully qualified domain name.

TXT

Text Record — A TXT record allows an administrator to insert arbitrary text into a DNS record.  The most common implementation of TXT records are for adding SPF records to a domain.