Denic (.DE Registry) has certain requirements for nameservers that can be applied to .DE domains. A minimum of 2 authoritative independent DNS is required. It means that the IP-addresses of each nameserver should differ by at least one number in any octet. Also, at least one of them must be connected via IPv4.

For example:

192.0.2.1 and 192.0.2.2 pair is valid (IPs differ in 1 digit here);

192.0.2.1 and 2001:db8:85a3::8a2e:370:7334 pair is also valid.

Denic has created the NAST tool where you can check if your nameservers are compatible with a .DE domain.

You need to enter the domain name in question and its nameservers into the corresponding fields. If no error is reported, you can then set these nameservers for your domain.

If you do get any error, you'll need to contact your DNS provider and show them the error messages to fix this situation.
What is the Personal DNS Servers option used for?

The Personal DNS servers option allows you to register your private nameservers.

EXAMPLE: If you have purchased the domain name yourexample.com, and your hosting company provided you with the IP addresses for personal nameservers, you will have an opportunity for your domain to be pointed to ns1.yourexample.com and ns2.yourexample.com.


NOTE: Once you have your nameservers registered, please do not forget to create the corresponding A records for them in your domain name zone file. This can be done in the DNS or Zone Management menu of your hosting control panel. You might need to contact your hosting company for assistance with setting up the records.