Howto reverse mapping ?

[Kevin Darcy]

John wrote:

> > The range of IP is 212.208.151.112 to 212.208.151.127....
> > What shall I do ? Shall I do a file for 151.208.212.in-addr.arpa ??
> >
>
> yes 151.208.212.in-addr.arpa will do with  IN PTR records for your ip
> addreses
>
> but for it to be successfully done you isp should also put in their
> 151.208.212.in-addr.arpa zone
>
> 112  IN NS  w.x.y.z
> 113  IN NS  w.x.y.z
> ...
> ...
> ...
> 127  IN NS  w.x.y.z
>
> where w.x.y.z is the DNS server serving your 151.208.212.in-addr.arpa zone

(I hope you weren't implying that "w.x.y.z" is an IP address, since that
would be illegal on the right-hand side of an NS record.)

You know, this scheme might actually work (although I haven't actually tried
it). Other nameservers would be fooled into thinking that there is a
112.151.208.212.in-addr.arpa zone, for example, send the PTR query to the
w.x.y.z server and get an authoritative answer. As long as they didn't look
too closely at the Authority Section, they'd probably just accept the answer
and go on their merry way.

But there is a fatal flaw in this scheme:

Only 1 NS is present for each pseudo-zone. For reasonable availability, you
should have at least 2. But your ISP is not likely to agree to adding and
maintaining 2 NS entries per address.

Why not go with the officially-sanctioned Best Practice of putting CNAMEs in
the /24 reverse zone?


- Kevin