Classless in-addr.arpa. Delegation

Classless in-addr.arpa. delegation allows network administrators to provide
authoritative reverse DNS on subnets that don't fall on octet boundaries.
This is especially useful for subnets comprised of less than eight bits in the
host portion of the address (i.e. smaller than a class C).

There are two important things to remember: first, we're dealing withclassless subnets, meaning they don't align themselves neatly with IPv4'soctet boundaries (like a class A, B, C, D, or E network); and...