add support for unknown-clients settings
diff --git a/isc_dhcp/files/dhcpd.subnets b/isc_dhcp/files/dhcpd.subnets
index 7305810..3e40bc2 100644
--- a/isc_dhcp/files/dhcpd.subnets
+++ b/isc_dhcp/files/dhcpd.subnets
@@ -14,6 +14,8 @@
   {%- if subnet.pxeserver is defined %}
   next-server {{ subnet.pxeserver }};
   {%- endif %}
+{%- if subnet.unknown_clients is defined %}
+  {{ subnet.unknown_clients }} unknown-clients;
+{% endif %}
 }
-
 {%- endfor %}