To ensure proper connectivity of your domain at the registry the following
technical quality guidelines must be adhered to in order to use own nameservers.


General
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All provided Nameservers must be reachable und authoritative for the zone.


Redundant connectivity
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At least two nameservers are required, where at least one of these must be
connected via IPv4. At least one Nameserver must be connected with an IP address
which is different from the IP addresses of all other nameservers.


Requirements for zone data
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The NS RRSet must exactly match the list of given nameservers. A CNAME record for
the zone is forbidden. The referral response must have a maximum size of 512 Bytes
to fit in a UDP packet.


Other requirements for the nameservers
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IPv6 addresses must be in the global unicast address range.