Cname of Cname

Mark_Andrews at Mark_Andrews at
Tue Dec 24 00:17:02 UTC 2002

> CNAMES of CNAMES are not allowed.
> -Steve

	Go re-read RFC 1034.  CNAME refering to CNAMES are specifically

5.2.2. Aliases

While attempting to resolve a particular request, the resolver may find
that the name in question is an alias.  For example, the resolver might
find that the name given for host name to address translation is an
alias when it finds the CNAME RR.  If possible, the alias condition
should be signalled back from the resolver to the client.

In most cases a resolver simply restarts the query at the new name when
it encounters a CNAME.  However, when performing the general function,
the resolver should not pursue aliases when the CNAME RR matches the
query type.  This allows queries which ask whether an alias is present.
For example, if the query type is CNAME, the user is interested in the
CNAME RR itself, and not the RRs at the name it points to.

Several special conditions can occur with aliases.  Multiple levels of
aliases should be avoided due to their lack of efficiency, but should
not be signalled as an error.  Alias loops and aliases which point to
non-existent names should be caught and an error condition passed back
to the client.

Mark Andrews, Internet Software Consortium
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: Mark.Andrews at

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