On Feb 26 2013, Tony Finch wrote:
Dickson, Brian <[email protected]> wrote:
[...]
Instead of delegating to omniscient AS112 servers, what about doing a
DNAME to a specific target "foo" (replace "foo" with what you will) in the
DNS tree?
Like this?
We have had (afaik) one interop problem with this setup: there was a mail
server on a network with DNAMEd reverse DNS, and some recipient sites
objected to this.
Including in particular those for c*m*a*t.n*t, to whom we wrote in March 2011
| It appears that your servers fail to cope with this sort of result,
| and respond with an immediate
|
| 421 [hostname] comcast Reverse DNS failure : Try again later
|
| to an SMTP connection.
|
| What surprises us is that they do not behave like this if reverse
| lookup returns just a CNAME and a PTR record, in the style originally
| envisaged by RFC 2317. The extra DNAME seems to make the difference,
| but it ought to be ignored if not understood, and the "synthesised
| CNAME" acted on instead.
We never heard back from them, and we had to paper over the problem
by replacing the DNAME for 233.232.128.in-addr.arpa with 256 CNAMEs.
Still, this shouldn't be an issue if the intent is to generate
a negative answer to a reverse lookup. More to the current point
is that (unfortunately) few DNS registries support putting DNAMEs
in parent zones in place of delegations.
--
Chris Thompson University of Cambridge Computing Service,
Email: [email protected] New Museums Site, Cambridge CB2 3QH,
Phone: +44 1223 334715 United Kingdom.
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