non-24 bit subnets

Alex McKenzie alex at chem.umass.edu
Wed Oct 6 20:15:22 UTC 2010


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David Miller wrote:
>  On 10/6/2010 3:21 PM, Jay Ford wrote:
>> On Wed, 6 Oct 2010, Alex McKenzie wrote:
>>> Unfortunately, we do have need -- or at least a use -- to have smaller
>>> subnets in multiple files, but without delegating authority.  The
>>> problem is that some of those small subnets should have a shorter TTL,
>>> or other settings changed.  If there's a way to change all the settings
>>> by host in a single file, that would at least make that easier.
>>
>> You could use one real zone file which is referenced by named.conf,
>> with $INCLUDE directives in that zone file to pull in the parts of the
>> zone from files containing the subsets you want.  A $TTL directive at
>> the top of each small file should give you the variable TTL defaulting
>> you want.
>>
> 
> You can have a different TTL for each and every record, if you like, in
> the same zone file with no includes (the $TTL directive can appear
> multiple times).
> 
> e.g. :
> 
> $TTL 300    ; 5 mins
> *    PTR    host-no-spec.example.com.
> $TTL 3600    ; 1 hour
> 17   PTR   mail.example.com.
> $TTL 1800    ; 30 mins
> 18   PTR   mail2.example.com.
> $TTL 86400    ;  1 day
> 19    PTR    whatever.example.com
> 20    PTR    whatever2.example.com
> 22    PTR    whatever2.example.com
> 
> ^^ This works for me.
> 
>>> For larger subnets we can use multiple zones, but I'd hoped to avoid it
>>> if possible.  It sounds from this like there isn't a way, though.
>>
>> Right.
>>

Interesting -- I'll keep that in mind.  I suspect I can make either that
or the INCLUDE directive work for me.


Out of curiosity:  what if it's a /16 or /8 network?  Do those also get
built as 24 bit files, or can they be built differently?  I seem to
recall seeing an option for a reverse lookup file with hosts declared as:

x.y	PTR	host.domain.tld.

Does that work, or was that an old format that's been deprecated, or
would it never have worked?

Thanks,
  Alex
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