Subnetted zones...

[Kevin Darcy]

Pelletier, Michael wrote:

> My company is becoming it's own Authoratative DNS (currently AT&T is doing
> external DNS for us). Anyway, my question is this; AT&T has given us a Class
> A address with a 255.255.255.128 netmask. How do I do the PTR zones when I
> can not make a zone complete zone (ie the netmask being 255.255.255.128). Do
> I have to make a seperate PTR zone for each machine?

You could do that, but it would be a pain to manage. Another way is to use the
RFC 2317 method, which just involves the parent zone putting aliases into their
zone pointing at PTR records you control. Read RFC 2317 liberally, though: the
PTRs can go into *any* zone that you control, they don't have to go into a zone
specifically delegated for the purpose. In fact, I think it's a fine idea to
put the PTRs into an existing "forward" zone, e.g. example.com. It really
doesn't matter what zone the PTRs go into: the zone is just acting as a
container and should be invisible to most clients doing reverse lookups. You
and AT&T will need to agree on a method of delegation, i.e. either delegating
each address as a zone or aliasing, and if you choose aliasing, where the
aliases will point. They may *insist* on following RFC 2317 literally, in which
case you may need to set up a special zone just for this purpose.


- Kevin