in-addr.arpa question

[Bret Ford]

Hi,

My ISP, at my request, recently delegated to me responsibility
for reverse name look up.  I have a DSL connection with 6 IPs (including
the gateway).  They did it this way (output from 'dig'):

 9.57.102.216.in-addr.arpa.  2H IN CNAME   9.8.57.105.216.in-addr.arpa.
10.57.102.216.in-addr.arpa.  2H IN CNAME  10.8.57.105.216.in-addr.arpa.
11.57.102.216.in-addr.arpa.  2H IN CNAME  11.8.57.105.216.in-addr.arpa.
12.57.102.216.in-addr.arpa.  2H IN CNAME  12.8.57.105.216.in-addr.arpa.
13.57.102.216.in-addr.arpa.  2H IN CNAME  13.8.57.105.216.in-addr.arpa.
14.57.102.216.in-addr.arpa.  2H IN CNAME  14.8.57.105.216.in-addr.arpa.

I haven't been able to get this to work.  Is it kosher to CNAME across
class B networks this way?  I'm rather new to this, so please pardon me
if that's a dumb question.  Assistance much appreciated!

Bret Ford