$TTL 300
1                IN PTR   foo.example.com.
2                IN PTR   bar.example.com.
3                IN PTR   baz.example.com.
4                IN PTR   silly.example.com.
5                IN PTR   willy.example.com.
6                IN PTR   billy.example.com.
7                IN PTR   my.example.com.
8                IN PTR   fair.example.com.
9                IN PTR   lady.example.com.