CNAME query

[Tony Finch]

Sonal Pahuja <sonal.s.pahuja at oracle.com> wrote:
>
> We are sending a CNAME query but currently we don't have any CNAME
> record, just have NS info. What should be the Bind9 response for this
> CNAME query? Will it return NS Record in Authority/Answer section?

In general, applications should not make CNAME queries because then they
have to implement their own CNAME-chasing logic which is fraught with
peril. Instead they should query for the final type the application needs,
and let the DNS server handle CNAMEs. (In fact, DNS resolvers also should
not make CNAME queries if they are looking for another type.)

If you query for CNAME at a delegation point, the result you get depends:

  * If the server is authoritative for the parent zone, but not the child
    zone, and does not offer recursive service, you will get a referral in
    response.

  * If it is a recursive server, and your query has RD=1 (recursion
    desired) you should get a NODATA/NOERROR response from the child zone.
    The exact contents of the response can depend on the server's
    implementation and/or configuration; see RFC 2308 for details.

  * If it is a recursive server, and your query has RD=0, then the
    response will depend on the contents of the server's cache.

Tony.
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