Having a Master/Slave DNS configuration, means that your DNS zone is transferred using AXFR to Slave name servers. Usually, these name servers are listed in the DNS configuration file on your Master server. However, using a DDoS Protected subscription at ClouDNS, automatically removes our Free servers as name servers available for you. This is due to security reasons if you are using a DDoS Protected subscription, you must have access only to DDoS Protected name servers. Unfortunately, you may still get AXFR requests from our Free servers. As these name servers are not listed anywhere else in your DDoS Protected account, they may seem unfamiliar to you.
Of course, it does not mean that all requests from unknown name servers are coming from our Free servers. In order to check, whether or not these servers are ours, there are 2 options: you can check, if there is a Reverse record for the IP address or contact our Technical Support Department with a list of all unknown IP addresses. In case you would like to check it by yourself, you can use the following command in Terminal:
$ host ip.address.of.server
To avoid getting warnings in your logs from our name servers, you can allow the zone transfer to them. Before doing it, we strongly advise to double check, do these name servers belong to ClouDNS. Please have in mind, that in reverse IP address lookup, all Free name servers must be in the following format:
ns*.cloudns.net
Note: Even if you allow the zone transfer to them, we do not recommend using these name servers as NS records in your DNS zone or as name servers at the domain name registrar.