Where is reverse DNS working?

Your provider needs to delegate the reverse DNS for the netblock to you. That's something that should be simple, and in some rare cases it is simple, but usually it's more complicated - your provider sets up a CNAME for each IP address that points at your nameserver.

As an example, if you're running 10.105.179.128/25 then your provider will add 128 CNAMEs, looking like this:

153.179.105.10.in-addr.arpa CNAME 153.128-25.179.105.10.in-addr.arpa

and some NS records:

128-25.179.105.10.in-addr.arpa. 86400 IN NS ns1.yournameserver.com.
128-25.179.105.10.in-addr.arpa. 86400 IN NS ns2.yournameserver.com.

And you'll create the zone 128-25.179.105.10.in-addr.arpa. on your nameserver and populate it with PTR records. Everything works perfectly.

There are several different ways of doing it. Hurricane Electric have a decent doc describing them here.

Your ISP must delegate your netblock to you. This will not work if you don't own a complete subnet, however small but just a few adresses in a larger block. In the latter case, your provider should offer some way to edit the reverse entries.