Root zone
These servers manage the DNS root zone
all servers delegate to
IN-ADDR.ARPA.
These servers manage the IN-ADDR.ARPA zone
all servers delegate to
121.in-addr.arpa.
These servers manage the 121.in-addr.arpa zone
all servers delegate to
18.121.in-addr.arpa.
These servers manage the 18.121.in-addr.arpa zone