[dns-operations] Any DNAME usage experience?

Tony Finch dot at dotat.at
Mon Mar 30 11:33:59 UTC 2020


Meir Kraushar via dns-operations <dns-operations at dns-oarc.net> wrote:
>
> I looking for insights, usage experience regarding DNAME record
> implementation. If any compatibility issues, client side problems,
> resolvers etc?.. Highly apperciate If anyone could share their
> knowledge.

At Cambridge University we're using DNAMEs for classless reverse DNS
delegation for shorter prefixes, originally to minimize the number of
zones when 128.232.128.0/17 was delegated, and more recently to handle the
way we split 10.0.0.0/9 for departments and 10.128.0.0/9 for the
University as a whole.

https://tools.ietf.org/html/draft-ietf-dnsop-rfc2317bis
https://www.dns.cam.ac.uk/domains/reverse/

It works OK except that we had problems with a mail server: some recipient
sites had buggy mailers that could not understand DNAMEs in the reverse
DNS so rejected mail. The problem was fixed by changing the mail server's
/24 to use a forest of CNAMEs instead of a DNAME.

I had wondered if DNAME support had improved enough in the last 10 years
to make this workaround unnecessary, but sadly it sounds like there are
still too many buggy resolvers :-(

There was also some annoyance with the glibc resolver: it would chatter
into syslog about unexpected records (i.e. DNAMEs) when parsing DNS
responses. This was fixed years ago.

Tony.
-- 
f.anthony.n.finch  <dot at dotat.at>  http://dotat.at/
Ardnamurchan Point to Cape Wrath: North or northwest, backing west or
northwest, 4 or 5. Moderate occasionally rough in north. Showers. Good.


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