# DNS Resource Records

Each [zonefile](/dns/zonefile) contains resource records:

|| border=1 align=center

||# Record Type ||# Description ||

||      A||IPv4 Address record || 

||   AAAA||IPv6 Address record ||

||  CNAME||Canonical Name: a name (an alias) which redirects to another a host. ||

||     MX||Mail eXchange record: includes a preference value for the mail server. ||

||     NS||Name Server ||

||    PTR||PoinTeR record: used to [reverse map](/DNS/RDNS) IP addresses to hostnames. ||

||    SOA||Start of Authority: provides the name of the zone, email address, and other data. ||

||    SRV||SeRVices record: lists the services available such as SIP, XMPP, LDAP, HTTP. This helps for discovering services. ||

||    TXT||TeXT record: any text can be provided with a name, such as an [SPF record](DNS/SPF) or a [[DKIM record](/DNS/DKIM) ||
||    TXT||TeXT record: any text can be provided with a name, such as an [SPF record](DNS/SPF) or a [[DKIM record](/DNS/DKIM) ||

## Creating DNS records

Each record in the zone file is written in this format:

Name TTL Class Type Data

    ; zone file for example.com
    $TTL 2d    ; 172800 secs default TTL for zone
    $ORIGIN example.com.
    @             IN      SOA   ns1.example.com. hostmaster.example.com. (
                            2003080800 ; se = serial number
                            12h        ; ref = refresh
                            15m        ; ret = update retry
                            3w         ; ex = expiry
                            3h         ; min = minimum
                            )
                  IN      NS      ns1.example.com.
                  IN      MX  10  mail.example.net.
    joe           IN      A       192.168.254.3
    www           IN      CNAME   joe