pfSense

I have network with 192.168.100.0/23 which would include hosts from 192.168.100 and 192.168.101. In such configuration for DHCPv4 server DNS update reverse domain is generated as:

zone 100-101.168.192.in-addr.arpa. {
primary 192.168.100.4;
key "ddns-key";
}

This 100-101 domain is completely bogus and not used by DHCP daemon at all (with the same effect you could put string blahblah there), so it tries to push changes to reverse domains without key which leads to rejection and fail. It could be easily fixed manually if DHCP server config would support custom config section but there is somebody way to smart decided that nobody needs that for DHCP server. So current solution either make DNS server wide open to updates on reverse zone or manual modification of source code which generates config.