This object controls whether DVMRP protocol messages on a tunnel interface are sent as unicast directly to the remote tunnel endpoint instead of through the tunnel's normal path. An admin enables this specifically to interoperate with mrouted-based systems or Cisco routers whose tunnels are configured in DVMRP mode, since those implementations expect unicast DVMRP messaging. For example, enabling this on a tunnel to a Cisco router running DVMRP would resolve neighbor-adjacency problems caused by a unicast versus multicast mismatch between the two implementations.