SLP is designed to use multicast for service discovery in the absence of DAs and for DA discovery. If your network does not deploy multicast routing, you can configure SLP to use broadcast by setting the net.slp.isBroadcastOnly property to True.
Unlike multicast, broadcast packets do not propagate across subnets by default. For this reason, service discovery without DAs in a non-multicast network works only on a single subnet. In addition, special considerations are required when deploying DAs and scopes on networks in which broadcast is used. A DA on a multihomed host can bridge service discovery between multiple subnets with multicast disabled. See DA Placement and Scope Name Assignment for more information on deploying DAs on multihomed hosts.