Default value for TTL

The record lifespan is set to 1 day by default.

$TTL            1D

Zone example.com

The zone is defined by:

• the serial number and the associated various delays (refresh, delay before retry, delay before expiration, minimum conservation time),
• the DNS servers necessary for managing the zone (NS),
• the servers dealing with the mails (MX) and a rule to define outgoing mail (SPF).

example.com.    IN      SOA    ns1.example.com. hostmaster.example.com. (
                                 2011040100     ; Serial
                                 2H             ; Refresh
                                 1H             ; Retry
                                 7D             ; Expire
                                 1D )           ; Minimum
                IN      NS     ns1.example.com.
                IN      NS     ns6.sample.net.
                IN      MX     10 mrelay1.example.com.
                IN      MX     20 mrelay1.sample.com.
                IN      TXT    "v=spf1 a:mrelay1.example.com ~all"

Localhost

The loopback called localhost is defined to avoid overloading the server of the zone above with requests that should stay local, and provide a greater security by defining ourselves the value of localhost.

; Myself
;----------------------------------------------------------------------
localhost       IN      A      127.0.0.1
                IN      AAAA   ::1

Name servers

One of the name servers (ns1.example.com) used to delegate the domain belongs to it.

; DNS
;----------------------------------------------------------------------
ns1             IN      A      192.168.1.5
                IN      AAAA   2001:db8:0:1::5

Remember that for the delegation it will be necessary to include this data. More information is available on the NS record.

Mail

Mail to be sent to the domain has been defined previously by the MX record, it is now necessary to provide the definition of the MX used for this domain (mrelay1), a rule describing outgoing mail will also be provided (SPF record) to limit spam. Mail will be read from a web interface (mail) and with a mail reader using the IMAP protocol (imap), sending mail is done with SMTP protocol (smtp). Distinction is done here between incoming and outgoing mails for the domain (mrelay1) and the mail sent by mail clients belonging to the domain (smtp).

Both SPF records here end in ~all (softfail) rather than -all, which is what a finished record should end in — Sender Policy Framework says why, and when to tighten it.

; Mail
;----------------------------------------------------------------------
mrelay1         IN      A      192.168.1.10
                IN      TXT    "v=spf1 a ~all"

mail            IN      A      192.168.1.10
                IN      AAAA   2001:db8:0:1::10
smtp            IN      CNAME  mail
imap            IN      CNAME  mail

Web and ftp

Two web servers and an ftp server are created. And the geographical location of the web server is specified.

; Web
;----------------------------------------------------------------------
www             IN      A      192.168.1.20
                IN      AAAA   2001:db8:0:1::20
                IN      LOC    45 45 8.15 N 4 52 20.17 E 180m 5m 5m 5m
piwik           IN      CNAME  www

; Ftp
;----------------------------------------------------------------------
ftp             IN      A      192.168.1.20
                IN      AAAA   2001:db8:0:1::20

Services

Names for the LDAP and Subversion services are defined.

; Other services
;----------------------------------------------------------------------
ldap            IN      A      192.168.1.5
                IN      AAAA   2001:db8:0:1::5
svn             IN      A      192.168.1.20
                IN      AAAA   2001:db8:0:1::20

Host

Two hosts in the domain are defined here, and their SSH fingerprints are published.

; Host
;----------------------------------------------------------------------
incal           IN      A      192.168.1.207
                IN      AAAA   2001:db8:0:1::207
                IN      SSHFP  1 2 2a5b5bb89d21ee5c100c15b82a99bfd9bf7926c1391bc35503a7a2256bdd5065
                IN      SSHFP  4 2 8cd6b552e0592dbd1c298032e4f9daf5ee1b180df499145edc818768f0559893

rork            IN      A      192.168.2.124
                IN      AAAA   2001:db8:0:2::124
                IN      SSHFP  1 2 601cb297804b94a369e514a9e2046d8dc35ceb1e045b25b6e58fe41a602e47b0
                IN      SSHFP  4 2 73c3323d7bccca800b191f68092736c5d8aa3fb782d7f4db47b601084288f810

Delegation

Zone delegation for the home zone is put into place with the NS records. Be careful, the following sample uses only one name server instead of the two advised.

; Delegation
;----------------------------------------------------------------------
home            IN      NS     ns1.example.com.