DNS RFC 2317 Question

I am trying to wrap my head around setting up our external reverse DNS and I just don't get it.  According to our ISP our network block has been delegated to our name servers.  I've tried multiple things and I just can't seem to make it work.

Let say the address range we were provided is 10.11.12.0/27.  How do I setup Bind 9.3x to handle the reverse DNS?  Here's snippets of my configuration (modified of course).

All of my zones and configs load without error.  But when I try and reverse the ip address 10.11.12.20 I get nothing.

I don't understand the hand off per RFC 2317 and how to setup our DNS.

Any help would be greatly appreciated.

Thanks!

/var/named/chroot/etc/named.conf
 
zone "0/27.12.11.10.in-addr.arpa" {
        type master;
        file "/var/named/10.11.12.rev";
        };
 
-------------------------------------------------
 
/var/named/chroot/var/named/10.11.12.rev
 
$TTL    86400
0/27.12.11.10.in-addr.arpa.   IN      SOA     ns1.example.com infrastructure@example.com. (
                        1236957449
                        10800
                        3600
                        604800
                        38400 )
        IN      NS      ns1.example.com.
        IN      NS      ns2.example.com.
20      PTR     email.example.com.