hote-a    IN  A      10.0.0.20
ftp       IN  CNAME  hote-a
www       IN  CNAME  hote-a

hote-a    IN  A      10.0.0.20
hote-b    IN  A      10.0.0.21
ftp       IN  CNAME  hote-b
www       IN  CNAME  hote-a