Pfsense dhcpd comes up authoritative, you can view the settings in the dhcpd.conf file.. But you are correct it is not sending NAK when it should since its authoritative. Is my understanding, but it seems you need a deny in the conf for that to happen. But that again is on ISC, I agree if the dhcp is set to be authoritative for a pool, it should not just ignore requests but actually NAK them if they are not good.
It will renew a lease, if its still in the pool even when here is a reservation setup for a client. Which is why I thought it would renew, but you are correct if you change the pool then that lease is no longer valid. But its not sending nak, so client will have to wait until lease expires before sending discover.
So a quick work around if you want to send NAK.. Is just create another pool that contains the ranges you want to NAK and then deny clients send a request for that - they will get a nak, and then send out discover vs waiting for their lease to expire.
There was a request long time ago to allow for custom changes to the conf file, like you can with unbound and the advanced box. It would be nice to be able to do that.. Another work around is just killing the dhcpd edit conf and then starting it directly pointing to your conf file and what interfaces you want it on. So that conf does not get rebuilt from the xml in the normal service startup.
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