dhcpd.conf logical hierachy

[Narcis Garcia]

In a Debian 9 host, I receive warnings like:
Dynamic and static leases present for 172.16.20.201.
Remove host declaration printer_1 or remove 172.16.20.201
from the dynamic address pool for 172.16.0.0/16

I'm trying to combine static reservations with dynamic assignment in
same subnet:

authoritative;
use-host-decl-names on;
server-name "equilibri.cpu.actiu.net";
subnet 172.16.0.0 netmask 255.255.0.0 {
        option routers 172.16.20.100;
        option broadcast-address 172.16.255.255;
        option domain-name-servers 172.16.21.61;
        option ntp-servers 172.16.20.100;
        pool {
                # IP range to be assigned dinamically
                range 172.16.20.150 172.16.20.189;
                allow unknown-clients;
        }
        pool {
                # IP range to be assigned statically
                range 172.16.20.0 172.16.20.149;
                range 172.16.20.190 172.16.20.255;
                deny unknown-clients;
#                deny all clients;
                group MyReservations {
                        host printer_1 {  # Impressora
                                hardware ethernet **:**:**:**:**:**;
                                fixed-address 172.16.20.201;
                                option host-name "printer_1";
                        }
                }
        }
}

But I've not clear if "group" and "host" work inside "pool", or what
else is the problem.