Use Conditional Forwarding but by network is 20 CIDR

[yubiuser]

We're waiting for the inclusion of one patch a Pi-hole Dev send upstream to dnsmasq

Support prefix /12 for conditonal forwarding

dnsmasq only supports the following prefix lengths: 8, 16, 24, 32. The line rev-server=172.16.0.0/12,172.16.0.4 specifies a netmark of /12 which is not allowed. This has nothing to do with your last assumption. This is documented in the dnsmasq man page (albeit poorly and only under the option domain): If the address range is given as ip-address/network-size, then a additional flag "local" may be supplied which has the effect of adding local declarations for forward and reverse DNS queries…