Checking Nameservers

Use this tool to check if your nameservers are configured correctly:

 


Example: dns.lu

 

 

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Technical Description

Before a domain name can be activated in the .lu zone, the name servers responsible for the domain name requested must be operational and configured correctly. The following five points are checked before a server is approved:

  • the name servers should answer authoritatively for the requested domain;
  • the name provided for the name servers must not be an alias (i.e. the data field of a CNAME record);
  • the name of the name server must correspond to the IP address provided;
  • the name server must be listed as a name server (IN NS record) for the requested domain;
  • the names of the name servers must comply with the definitions given in the RFCs.

Technically, two different configurations are possible.

a) The name server is part of the domain it is serving (e.g. ns1.dns.lu is part of the dns.lu domain). A type A query requesting the name of the name server is sent to the server’s IP address. The response from the server must be authoritative, contain the server’s IP address and must not return the server name in the form of an alias. The second stage in the validation involves an NS query being sent to the server’s IP address for the domain name in question. The response to this query must also be authoritative and contain the name of the name server.

b) The name server is not part of the domain it is serving. An NS query for the domain is sent to the IP address obtained through normal resolution of the name of the server name (and not to the IP address on the form). The query must be authoritative and contain the name of the queried server. A type A query requesting the name of the name server is then sent to any name server that is able to perform recursive resolutions. The response must contain the name server’s IP address as given on the form. In addition, the name of the name server must be a canonical name and not an alias (CNAME).  All the queries referred to above are sent as UDP datagrams and are resent three times at four-second intervals before a server is considered to be uncontactable.

 

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dns.lu - aspects techniques et juridiques des noms de domaine