Anyone from AT&T DNS?

Mark Andrews marka at isc.org
Mon Oct 9 01:42:48 CST 2017


In message <CAN414UfOQH-rOsJ4V_idiv-2UQi0jVM=w5AOs6HmnA-NkDvESg at mail.gmail.com>, Jay Farrell via NANOG writes:
> Yep, the notation with the slash used to be ATT's standard method. At my
> job (where we had some customers with ATT MIS T1 circuits) we transitioned
> to a web front end for our DNS that didn't allow for the slash, so we had
> to nudge ATT to allow us to use a dash notation instead for delegations.
> 
> As far as to what can appear in a DNS entry, you'd be amazed. I encountered
> a PTR record containing a full URL, http:// and everything; it didn't
> actually work of course, but bind allowed it to exist. When I tracked down
> the cow-orker who had entered it, he said he knew it wasn't valid, but he
> did it that way when the customer insisted it had to be thus. :-D

DNS labels can be octet string [0..63] with the zero length octet
string being being reserved or the root label and '*' for the
wildcard label (there is no way to turn this off).

Hostnames on the other hand are restricted to LDH.

Unfortunately many tools are not written by people who understand
the difference.  Additionally lots of administrators also don't
know the difference.  They also often don't understand why hostnames
are restricted to LDH.

Mark
-- 
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: marka at isc.org


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