PTR vs CNAME?

[Kevin Darcy]

Eric N. Moyer wrote:

> Why is PTR used for reverse mapping instead of CNAME?  Thanks.

Some providers prefer to delegate individual addresses as separate
reverse zones. You'd never be able to do that if the "leaf" nodes for
reverse DNS were CNAMEs, because of the infamous "CNAME and other data"
rule.

Note that under RFC 2317, it is possible to use CNAMEs in conjunction
with PTRs for reverse mapping, so the two aren't really mutually
exclusive. But the CNAMEs aren't functioning as "leaf" nodes in that
case, and the methodology is incompatible with the delegation of
individual addresses as separate zones.


- Kevin