Why is my domain not showing up yet?: " if you want to know the host name corresponding to 126.96.36.199, you would first ask the in-addr.arpa nameserver for 188.8.131.52.in-addr.arpa. The in-addr.arpa nameserver could then hand off your request to the 207.64.in-addr.arpa nameserver. That server might in turn hand off the query to the 129.207.64.in-addr.arpa nameserver, which would finally give you your name.
To set a custom reverse DNS record for your IP address, your registrar or host must allow you to control its DNS. The file with the reverse DNS record is known as a reverse zone file."
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