$TTL 1D
@       IN SOA  ns.ict.jp. root.ns.ict.jp. (
                                        20141120        ; serial
                                        1D      ; refresh
                                        1H      ; retry
                                        1W      ; expire
                                        3H )    ; minimum
        IN      NS      ns.ict.jp.
50.1.168.192.in-addr.arpa.        IN      PTR     ns.ict.jp.
110.1.168.192.in-addr.arpa.        IN      PTR    host110.dom110.ict.jp.
120.1.168.192.in-addr.arpa.        IN      PTR    host120.dom120.ict.jp.
130.1.168.192.in-addr.arpa.        IN      PTR    host130.dom130.ict.jp.
140.1.168.192.in-addr.arpa.        IN      PTR    host140.dom140.ict.jp.
150.1.168.192.in-addr.arpa.        IN      PTR    host150.dom150.ict.jp.
160.1.168.192.in-addr.arpa.        IN      PTR    host160.dom160.ict.jp.