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DNS Zonendatei/en

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Example of a zone file using the Hetzner Standard Template

The following zone file has been compiled for the domain "grossefirma.de":

$TTL 86400
@ IN SOA ns1.first-ns.de. postmaster.robot.first-ns.de. (
     2000091604  ; Serial
     14400       ; Refresh
     1800        ; Retry
     604800      ; Expire
     86400  )    ; Minimum

@           IN NS    ns1.first-ns.de.
@           IN NS    robotns2.second-ns.de.
@           IN NS    robotns3.second-ns.com.

localhost   IN A     127.0.0.1
@           IN A     1.2.3.4
www         IN A     2.3.4.5
mail        IN A     2.3.4.5

loopback    IN CNAME localhost
pop         IN CNAME www
smtp        IN CNAME www
relay       IN CNAME www
imap        IN CNAME www
ftp    3600 IN CNAME ftp.anderedomain.de.

@           IN MX 10 mail

technik     IN A     5.6.7.8
technik     IN MX 10 technik

@           IN TXT   "v=spf1 mx -all"

SOA record

$TTL 86400
@ IN SOA ns1.first-ns.de. postmaster.robot.first-ns.de. (
     2000091604  ; Serial
     14400       ; Refresh
     1800        ; Retry
     604800      ; Expire
     86400  )    ; Minimum
  • The dns zone has a TTL (Time To Live) of 86400 seconds ($TTL 86400)
  • The nameserver "ns1.first-ns.de" is responsible for the internet domain (the @ character is a placeholder for the domain "grossefirma.de" itself)
  • The period at the end of "ns1.first-ns.de." prevents the primary nameserver from being called "ns1.first-ns.de.grossefirma.de"
  • The email address for the Administrator is "postmaster@robot.first-ns.de" (the first period is always replaced by the @ character)
  • The zone file was last changed on 16.09.2000, this was the fourth change made on that day
  • The secondary nameserver undertakes changes from the primary nameserver every four hours (TTL = 14,400 seconds; Time To Live).
  • In the event of error, the secondary nameserver attempts synchronization again after 30 minutes (1800 seconds)
  • Should the secondary nameserver not have created synchronization with the primary nameserver after 7 days (604800 seconds), it declares the domain invalid
  • The entries are normally valid for 24 hours (86400 seconds), if no other value is defined
  • Other nameservers remember "negative" answers, so requests for non-existant hosts are likewise 24 hours

Nameservers

@           IN NS    ns1.first-ns.de.
@           IN NS    robotns2.second-ns.de.
@           IN NS    robotns3.second-ns.com.
  • The "ns1.first-ns.de", "robotns2.second-ns.de" and "robotns3.second-ns.com" are responsible for the nameservers
  • The period at the end of the lines here also prevents the search for "ns1.first-ns.de.grossefirma.de", which in this case would be nonsense
  • IP addresses are not permitted in NS records (if an own nameserver is used, whose hostname should be "ns1.grossefirma.de": define the appropriate A record and specify Glue when registering the domain and register the nameserver) in advance with the Registrars.

Hosts

localhost   IN A     127.0.0.1
@           IN A     1.2.3.4
www         IN A     2.3.4.5
mail        IN A     2.3.4.5
  • "localhost.grossefirma.de" is resolved as loopback address "127.0.0.1"
  • Enquiries, for example in the web browser, for "grossefirma.de" (without "www.") are resolved to "1.2.3.4"
  • "www.grossefirma.de" has the IP address "2.3.4.5"
  • A host called "mail.grossefirma.de" exists, but it is not clear from this entry whether this is also the responsible mail server

Aliases

loopback    IN CNAME localhost
pop         IN CNAME www
smtp        IN CNAME www
relay       IN CNAME www
imap        IN CNAME www
ftp    3600 IN CNAME ftp.anderedomain.de.
  • "localhost.grossefirma.de" can also be controlled as "loopback.grossefirma.de"
  • "www.grossefirma.de" has the following additional names "pop.grossefirma.de", "smtp.grossefirma.de", "relay.grossefirma.de" and "imap.grossefirma.de"
  • "ftp.grossefirma.de" is forwarded as "ftp.anderedomain.de", as the period at the end prevents resolution to "ftp.anderedomain.de.grossefirma.de"
  • "ftp.grossefirma.de" is valid for one hour only (3600 seconds), therefore changes to the entries become known relatively quickly to the nameservers on the world-wide Internet. Important: as long as the secondary nameserver still publishes the old values, this results in a delay in possible changes to the data, therefore the Refresh time should also be shortened in the SOA record

Note: if a subdomain already has a CNAME record, then no further record types can be set for this subdomain.

Mail servers

@           IN MX 10 mail
  • There is only one mail server and this is "mail.grossefirma.de"
  • IP addresses are not allowed for MX records
  • CNAME's are not allowed in MX records, only as aliases for A records
  • Further mail servers could be listed in an additional line, but this doesn't often make much sense
  • With several mail servers, the one with the least priority (here 10) is given preference

"Sub domain"

technik     IN A     5.6.7.8
technik     IN MX 10 technik
  • A "sub domain" is created within the zone file, however without being delegated to an external nameserver.
  • The host "technik.grossefirma.de" is responsible for the sub domain "technik.grossefirma.de", which resolves to IP address 5.6.7.8.

TXT records

@ IN TXT "v=spf1 mx -all"

Delegation of a subdomain to a new zone

As an alternative to the procedure described under "Sub domain", a delegation of subdomains to another DNS server is possible.

Note: In Robot, it is not possible to create DNS zones for subdomains! Here subdomains can only be defined as described in the section "Sub domain".

For example, a subdomain for the "technology" department of a large company needs to be setup for short-term internal tests. The DNS records of the subdomain need to be independent of the entries for the domain "grossefirma.de" (hosted at a large and possibly inflexible provider).

Preparing the main domain

In the zone file of the domain "grossefirma.de" the following entries are added:

technik     IN NS    ns.technik
ns.technik  IN A     5.6.7.8

This lets name server queries for, as an example, "www.technik.grossefirma.de" be passed on to "ns.technik.grossefirma.de". Since this host name should be resolved even by this same name server in the parent domain a "glue record" is entered: ns.technik.grossefirma.de -> 5.6.7.8.

Configuring the Zone File for the new Subdomain

On the new name server a zone file needs to be created for the new subdomain:

@ 86400 IN SOA ns1 admin (
     2000091604  ; Serial
     14400       ; Refresh
     1800        ; Retry
     604800      ; Expire
     86400  )    ; Minimum

@           IN NS    ns.technik
ns          IN A     5.6.7.8

@           IN MX 10 mail
mail        IN A     2.3.4.5

www         IN A     2.3.4.5

The administrator has the email address "admin@technik.grossefirma.de".

  • The primary name server has the hostname "ns.technik.grossefirma.de".
  • It is the only name server (there are no secondary name servers).
  • It has the IP address "5.6.7.8".
  • A host "mail.technik.grossefirma.de" with the IP address of "2.3.4.5" exists and is also responsible for the receipt of the subdomain mail.
  • There is another host named "www.technik.grossefirma.de" which resolves to "2.3.4.5".


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