Ignoring existing leases over Option 82 details

[Justin Shore]

Greetings.  It's been a long while since I was on this list.

We've configured a dhcpd install for our new FTTH deployment.  We have 
about 1500 classes and single IP pools defined, one for each ONT. 
Rather than assign a static IP to each ONT by matching the MAC address, 
we're using option 82 info set by the upstream OLT.  This will allow a 
tech in the field to replace a bad ONT without making any changes to the 
DHCP config.  This is the recommended method from the FTTH manufacturer.

We ran into a problem this afternoon during pre-deployment ONT upgrades. 
  A tech connected 10 ONTs to an OLT and did a code upgrade on them. 
The first 10 upgrades went well.  Then the tech disconnected those 10 
ONTs and replaced them with 10 new ones.  These 10 ONTs were connected 
to the same physical ports on the OLTs so they should have pulled down 
the same IPs as the first 10 ONTs.  However none of the new ONTs pulled 
IPs.  I determined from the log file that the problem was that the lease 
for the prior ONT was preventing dhcpd from reassigning that IP to the 
new ONT (based on logged DISCOVER message citing "no free leases" as the 
cause).  This would prevent a tech in the field from being able to swap 
out a bad ONT without someone kicking the DHCP server.  That defeats the 
purpose.  I deleted the 10 old leases in question and all the ONTs 
pulled IPs as expected.

So, my question is how I configure dhcpd to ignore an existing lease 
when option 82 information is available in a DISCOVER.  Is there a 
better way to accomplish our goals that would prevent this problem?  The 
ONTs have to get a static IP and they can not be manually configured. 
Techs in the field need to be able to swap ONTs at will without calling 
into operations to have someone change a MAC in the DHCP config.

Thoughts?  Thanks
  Justin