Classless IN-ADDR.ARPA delegation

[Kevin Darcy]

Henrik Samal wrote:

> 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?

I assume you mean "replace" rather than "add", right? If they already have PTR records for your addresses, then they won't be able to add CNAMEs with the same names...

> 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.

You'll need some leading whitespace for those NS records, otherwise they'll be misinterpreted.

> 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 ?

If it's configured as a slave, yes. If it's not, then it'll be lame since your ISP delegated the 120-127.31.13.217.in-addr.arpa zone to it.

                                                                                                                - Kevin