DNS REQUIREMENTS FOR .NL:
Each domain shall have a primary name server and at least one secondary
name server. The name servers stated for incorporation in the NL zone file
should preferably be located in different (sub) networks.
The name servers stated for incorporation in the NL zone file should be
accessible from anywhere on the Internet.
Zone transfers may be blocked if desired, but shall be open at least to the NL
primary name server host. This is necessary for (regular) checks of the name
servers. It should be pointed out that blocking of zone transfers usually
provides only a semblance of security.
Prior to a domain being registered, the NL zone file
manager checks all name servers. This check includes name servers that have
not been stated, but are (evidently) incorporated in the zone file of the
domain concerned. Attention will be paid especially, but not exclusively, to
the following items:
The NS records of the zone file shall contain at least the stated name
servers;
Primary name server according to [field #4 of] the Server of Authority (SOA)
record shall be identical to that in the NS record and in accordance with
the statement;
The SOA, NS and MX records may refer to objects with an A record only,
not to objects with a CNAME record;
In view of the provisions under item 4, the zone file shall contain an MX
record (or an A record) for the domain proper;
Fallback MX records may not refer to third parties without permission
being granted by those third parties; in case of doubt the NL zone file
manager can verify this with the third party in question;
According to the standards a glue (A) record is incorporated in the NL
zone file for each name server host at any sub-domain level under the .NL
domain; if a name server for a domain is operated from a host of the
provider involved, the host name as it is known with the provider shall be
included in the zone file and the statement; the domain name in question may
not be included in the zone file, to prevent pollution of the NL zone file
by unnecessary glue records as well as problems in case the IP address of
such a name server host should change;