How to configure multiple domains on a single delgation?

[Jim]

For discussion purposes:
  1) a.b.c.d/29 classless delegation
  2) a.b.c.1 is the delegation address (network)
  3) a.b.c.2 is not assigned or used.
  4) a.b.c.3 thru a.b.c.6 will be A.domain
  5) a.b.c.7 will be B.domain
  6) a.b.c.8 is the broadcast address.

Does the ISP have to create CNAME records for each domain?

Or, as the ISP states:
  We have delegated your addresses to NS.A.domain. If you want to
  run a second domain, NS.A.domain is the authority for B.domain.

This does not seem correct to me. a.b.c.1 points to a.b.c.3 as
A.domain. A.domain cannot reference B.domain in the zone file.

Creating a nameserver on B.domain will do everything except a
reverse lookup as there is no glue record between it an ISP.

Or is my understanding that lacking?

Jim

-- 

Quidquid latine dictum sit, altum viditur.