Some DNS services have up to 4 nameservers (Mydomain, Everydns, Afraid.org) so provide all these servers in your application.
2. Some webhosting companies have nameservers that are unacceptable e.g. ns1.abc.com xxx.xxx.xxx.215 and ns2.abc.com xxx.xxx.xxx.216. These nameservers are within the same C block and in most cases at the same location resident on the same computer server.
3. It is your responsibility to furnish correct nameservers otherwise delays in changes will occur and with the registration of domains the deletion of your application.