[dns-operations] /24 Reverse DNS delegation using the IP Address 4th octet?

Doug Barton dougb at dougbarton.us
Tue Mar 16 21:23:56 UTC 2010

On 03/16/10 14:17, Chuck Anderson wrote:
> Ok, so I asked for a reverse DNS delegation of a /24.  Let's call it 
> "" for the sake of discussion.  I was expecting to get the 
> following in their (parent) zone:
> 2.1.10.in-addr.arpa. 86400	IN	NS	my-master-1.example.com.
> 2.1.10.in-addr.arpa. 86400	IN	NS	my-master-2.example.com.
> Instead, what they gave me was this:
> 86400	IN	NS	my-master-1.example.com.
> 86400	IN	NS	my-master-2.example.com.
> 86400	IN	NS	my-master-1.example.com.
> 86400	IN	NS	my-master-2.example.com.

Looks like someone either doesn't understand the difference between RFC
2317 delegation and "normal" delegation, or they have a
one-size-fits-all template and don't do a lot of netmask < /25 delegations.

> Is that workable?  It seems silly to me.  Can I still just set up a 
> single zone file like so?

Yes, but in named.conf you'll have to have 256 separate zone statements.
They can all point to the same zone file, but if the zone file has 255
"spurious" entries (because the zone for 0.* doesn't care about anything
other than the entry for 0, for example) you'll waste some memory in the

Better to go back to the parent and request a proper /24 delegation.




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