Al Stu wrote: >BIND 9.6 ‘named’ throws the following message during startup claiming >that it is illegal to use a CNAME/alias in the MX record. >I beg to differ. There is no such standard nor requirement prohibiting >the use of CNAME/alias in an MX record. > >Some people seem to think RFC 974 creates a standard which prohibits >the use of CNAME/alias in MX records. But very much to the contrary >RFC 974 demonstrates that CNAME/alias is permitted in MX records. > >ISC’s message that a CNAME/alias in an MX record is illegal is incorrect >and just an attempt by ISC to get people to go along with what is only a >perceived rather than actual standard/requirement, and should be removed >so as not to further the fallacy of this perceived perception of a >standard/requirement, as it is neither a standard nor a requirement, and >certainly not illegal.
checking RFCs published within the last 12 years might have been useful RFC2181: Clarifications to the DNS Specification this was published as Standards Track it's true that many RFCs were not advanced but the DNS Extensions Working Group is making an effort http://www.ietf.org/html.charters/dnsext-charter.html Jun 2007 Start of process of reviewing the following RFCs and to move them to Draft Standard status that not only includes rfc2181, but ones defining EDNS0, notify, negative caching, dynamic updates, SRV records etc 10.3. MX and NS records The domain name used as the value of a NS resource record, or part of the value of a MX resource record must not be an alias. Not only is the specification clear on this point, but using an alias in either of these positions neither works as well as might be hoped, nor well fulfills the ambition that may have led to this approach. This domain name must have as its value one or more address records. Currently those will be A records, however in the future other record types giving addressing information may be acceptable. It can also have other RRs, but never a CNAME RR. Searching for either NS or MX records causes "additional section processing" in which address records associated with the value of the record sought are appended to the answer. This helps avoid needless extra queries that are easily anticipated when the first was made. Additional section processing does not include CNAME records, let alone the address records that may be associated with the canonical name derived from the alias. Thus, if an alias is used as the value of an NS or MX record, no address will be returned with the NS or MX value. This can cause extra queries, and extra network burden, on every query. It is trivial for the DNS administrator to avoid this by resolving the alias and placing the canonical name directly in the affected record just once when it is updated or installed. In some particular hard cases the lack of the additional section address records in the results of a NS lookup can cause the request to fail. Danny _______________________________________________ bind-users mailing list bind-users@lists.isc.org https://lists.isc.org/mailman/listinfo/bind-users
