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Re: DNS: MX and CNAME records



On Sat, Jul 14, 2007 at 08:09:15PM +0200, martin f krafft wrote:
> my understanding of CNAME records is that an MX may not be a CNAME
> record, but I thought something like
> 
> users=> select * from pdns.records where name like 'wall.%';
>  domain_id |       name       | type  |      content       |  ttl  | prio | change_date 
> -----------+------------------+-------+--------------------+-------+------+-------------
>          8 | wall.madduck.net | CNAME | oerlikon.no-ip.org | 86400 |      | 
>          8 | wall.madduck.net | MX    | a.mx.madduck.net   | 86400 |   10 | 
>          8 | wall.madduck.net | MX    | b.mx.madduck.net   | 86400 |   99 | 
> 
> should be possible. Yet, dig (and bind9 host) don't like it:

Quote the RFC 2181:

: 10.1. CNAME resource records
:
: [...] An alias name (label of a CNAME record) may, if DNSSEC is in
: use, have SIG, NXT, and KEY RRs, but may have no other data. [...]

Yeah, it looks like CNAME excludes other RRs. I did not know that
either, but I guess it does make sense. Choosing which records
override which could get complicated if CNAME could be mixed with
other data.

Though I do not know if that is actually a problem for existing
software.



-- 
Tmi Juha-Matti Tapio    Puh/Tel. +358-50-5419230
Y-tunnus 1911527-0      Fax      +358-9-34756631

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