Reverse records in /22 network

[/dev/rob0]

On Thu, Mar 19, 2015 at 04:10:16PM +0000, Simon Hobson wrote:
> "Cuttler, Brian (HEALTH)" <brian.cuttler at health.ny.gov> wrote:
> 
> > Machines register in DHCP, and I see A and PTR records appear in DNS.
> > 
> > However, I'm using a /22 address space, 10.57.36-39.0 and I only 
> > declared a single pointer database
> > 
> > Zone "36.57.10.in-addr.arpa." in {
> > Type slave;
> > Masters {xx.xx.xx.xx};
> > File "db.esp122-ptr";
> > };
> > 
> > And I now wonder if I don't also need tables for 
> > 37.57.10.in-addr.arpa and 38 and 39 as well.
> 
> Yes you do. Any mask shorter than 24 bits is OK - you just have 
> multiple reverse zones (unless the mask is 8 or 16 bits long). It's 
> only when you have a mask longer than 24 bits that things become 
> more difficult.

It would be simpler for Brian to just take the whole /16 zone, 
57.10.in-addr.arpa, unless other parts of his extended internal 
network are using those addresses.  (And in that case, delegation 
should have been done.)

> > And then how to properly declare in dhcpd.conf.
> 
> Just declare zones for the extra three zones in the DNS - the same 
> as the one I assume you already have declared for 
> 36.57.10.in-addr.arpa

> Actually dhcpd will work out the right server to update is all the 
> delegation is done correctly - ie a lookup on the SOA for (eg) 
> 36.57.10.in-addr.arpa returns the correct master server. You only 
> need to define zones to either a) provide a key for secure updates, 
> or b) of the DNS isn't setup correctly and you need to tell dhcpd 
> where to send updates.
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