Classless IN-ADDR.ARPA delegation

[Henrik Samal]

Hello 

We have been delegated a subnet of 8 IP addresses fom our ISP (217.13.31.120-127). The ISP is already doing reverse, but we want to controll the reverese ourself. So basically all the ISP has to do is to add CNAME records in their "31.13.217.in-addr.arpa" zone pointing to our nameserver, right?

This could be something like this:

120-127  NS ns.mydomain.no.
              NS ns.someotherdomain.no.

120 CNAME  120.120-127
121 CNAME  121.120-127
...
127 CNAME  127.120-127

But how would our "120-127.31.13.217.in-addr.arpa." zone look like?

Maybe somthing like this: (?)

$TTL 6h 
120-127.31.13.217.in-addr.arpa.        IN      SOA     ns.mydomain.no. admin.mydomain.no.  (
                                1               ; Serial
                                6h              ; Refresh
                                3h              ; Retry
                                1w              ; Expire
                                1h )            ; Minimum
                
NS ns.mydomain.no.
NS ns.someotherdomain.no.

120 PTR host.mydomain.no.
121 PTR host1.mydomain.no.
...
127 PTR host7.mydomain.no.


Does this mean that ns.someotherdomain.no would transfer zone date from ns.mydomain.no when i update its "120-127.31.13.217.in-addr.arpa." zonefile ? 

Thanks,

Henrik