DHCP DDNS and BIND on non /24 reverse delegation

[M. Yu]

Hello list,

We've been allocated a /25 IP block by our provider and they are delegating
reverse DNS lookup for it by making us specify
128/25.177.110.64.in-addr.arpa in named.conf with allow-update set for DDNS.
I created the host file with no entry in it except for the SOA and NS RRs.
Now comes the problem.  When I recently checked the host file, it seems that
DDNS has wreaked havoc all over it by assuming that all entries there
belonged to a /24 (it sticks a $ORIGIN there) which is wrong since we're
only authoritative for the upper /25 of our IP block.

I am not sure who is messing with our host file: dhcp (3.0b2pl16-1 rpm from
Charles Anderson) or BIND (8.2.3 rpm from RH).  I know these are old
versions and I am about to move up but I need to be sure this problem can be
solved.  As I've said, I don't know who's messing the config so I'm
cross-posting this message to both the bind-users and dhcp-server lists.
Anyway, whichever it is that's re-writing the host file, how can I solve
this problem?  Is there a method of specifying what $ORIGIN to put or maybe
stop it from sticking things in the host file except for the DDNS update
itself (hostname+domain and IP address)?

Thanks!

M. Yu