The .LU registry requires that name servers are properly preconfigured before delegating the domain. This rule applies to both domain registration and modification of name servers.
The registry provides a web-based tool to check the DNS setup for a domain. The test shows whether there are setup errors for one or more name servers:
https://dns.lu/en/domains/name-server-test
You can enter both, the domain and the name servers for the test, as shown in the picture below:
Technical name server requirements
The .LU registry requires that:
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The name servers are authoritative for the requested domain.
- The name servers match the IP address provided.
- The name servers are listed as name servers (IN NS record) in the DNS zone of the domain.
- The name provided for the server names is a Canonical Name, not CNAME record.
Also, different validation steps apply depending on the name server configuration submitted:
If the name server is part of the domain name, for instance ns1.example.lu is part of example.lu, then:
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An 'A' query requesting the name server's name is sent to the server's IP address.
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The server's response must be authoritative and contain the server's IP address, and not return the name of the server in the form of an alias.
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An 'NS' query requesting the domain name in question is sent to the server's IP address.
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The response must be authoritative and contain the server's name.
If the server name is not part of the domain, then:
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An 'NS' query requesting the domain is sent to the IP address obtained by normal resolution of the server name (and not the IP address indicated in the 'IP Address' field).
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The response must be authoritative and contain the queried server's name.
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An 'A' query requesting the server name is sent to any server name that can handle recursive resolutions.
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The response must contain the IP address of the server name as indicated in the 'IP Address' field, and the server name must be a Canonical Name (CNAME).
If there is a failure, the servers are considered non-functional.