Reverse lookup for classless networks
Grant Taylor
gtaylor at tnetconsulting.net
Fri Dec 28 01:25:33 UTC 2018
It has come to my attention that my answer to the following question
might not have been clear. So I'll try again.
First I want to be clear that I was discussing what the records should
be, RFC 2317 Classless IN-ADDR.ARPA Delegation (read: CNAME) or standard
NS delegation. I don't care how the records (CNAME or NS) are
generated. I care what the records are, CNAME vs NS.
On 12/27/18 11:24 AM, John Levine wrote:
> PS: What's wrong with using $GENERATE in the parent zone like everyone
> else who uses BIND does?
I have zero problems with actually using $GENERATE in the parent zone
(or anywhere else).
I do have concerns about using $GENERATE to describe a concept to
someone who may not be as familiar with DNS, or BIND, much less
$GENERATE. As such, I tend to not use $GENERATE when answering questions.
Take the following examples. Which do you think someone that is new to
DNS will have an easier time understanding?
--8<--
$GENERATE 1-4 $ CNAME $.bob.example.net.
$GENERATE 5-8 $ NS ns1.example.com.
-->8--
Or
--8<--
1.localhost. 604800 IN CNAME 1.bob.example.net.
2.localhost. 604800 IN CNAME 2.bob.example.net.
3.localhost. 604800 IN CNAME 3.bob.example.net.
4.localhost. 604800 IN CNAME 4.bob.example.net.
5.localhost. 604800 IN NS ns1.example.com.
6.localhost. 604800 IN NS ns1.example.com.
7.localhost. 604800 IN NS ns1.example.com.
8.localhost. 604800 IN NS ns1.example.com.
-->8--
IMHO, the latter is easier to understand. As a bonus, it conforms to
standard zone file format. Something that any DNS administrator should
be able to recognize and interpret. I'm unwilling to say the same about
$GENERATE.
I trust that people that are comfortable with $GENERATE will recognize
it's use case when they see it.
I learned a long time ago to think about how the person learning
receives and understands things. As such, if there is a simple change I
can do as a teacher to make it easier for them as the student learn,
then I should do that.
--
Grant. . . .
unix || die
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