any device completing macsuck/arpnip must have that layer

lib/App/Netdisco/Worker/Plugin/Macsuck/Nodes.pm

@@ -92,7 +92,10 @@ register_worker({ phase => 'main', driver => 'snmp' }, sub {
   debug sprintf ' [%s] macsuck - removed %d fwd table entries to archive',
     $device->ip, $archived;
 
-  $device->update({last_macsuck => \$now});
+  $device->update({
+    last_macsuck => \$now,
+    layers => \[q{overlay(layers placing '1' from 7 for 1)}],
+  });
   return Status->done("Ended macsuck for $device");
 });