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ru.unix.bsd
- RU.UNIX.BSD ------------------------------------------------------------------
From : Valentin Nechayev 2:5020/400 08 Jul 2004 09:38:10
To : Spartak Radchenko
Subject : Re: mail & RFC
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>>> Spartak Radchenko wrote:
vs>>> Прямой запрет есть, но на него все клали. В RFC821.
vs>>> 5.2.2 Canonicalization: RFC-821 Section 3.1
DM>> Мимо. Это про CNAME на MX а не про MX на CNAME.
SR> Кстати, да. А я даже не посмотрел. Так есть ли где-нибудь явный
SR> запрет прописывать в качестве MX CNAME? Я пока не нашёл.
RFC974 (собственно описание для чего делаются MX'ы):
==={{{
Note that the algorithm to delete irrelevant RRs breaks if LOCAL has
a alias and the alias is listed in the MX records for REMOTE. (E.g.
REMOTE has an MX of ALIAS, where ALIAS has a CNAME of LOCAL). This
can be avoided if aliases are never used in the data section of MX
RRs.
===}}}
RFC1912:
==={{{
Don't use CNAMEs in combination with RRs which point to other names
like MX, CNAME, PTR and NS. (PTR is an exception if you want to
implement classless in-addr delegation.) For example, this is
strongly discouraged:
podunk.xx. IN MX mailhost
mailhost IN CNAME mary
mary IN A 1.2.3.4
[RFC 1034] in section 3.6.2 says this should not be done, and [RFC
974] explicitly states that MX records shall not point to an alias
defined by a CNAME. This results in unnecessary indirection in
accessing the data, and DNS resolvers and servers need to work more
to get the answer. If you really want to do this, you can accomplish
the same thing by using a preprocessor such as m4 on your host files.
===}}}
RFC1034 (он же STD13):
==={{{
Domain names in RRs which point at another name should always point at
the primary name and not the alias. This avoids extra indirections in
accessing information. For example, the address to name RR for the
above host should be:
===}}}
-netch-
--- ifmail v.2.15dev5.3
* Origin: Dark side of coredump (2:5020/400)
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