Reverse records in /22 network

Simon Hobson dhcp1 at thehobsons.co.uk
Thu Mar 19 16:10:16 UTC 2015


"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.

> 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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