While ip forward-protocol is an essential part of getting the router to forward an port that is not one that is forwarded by default, I read the original question slightly differently. I believe he was asking if the packet can be forwarded to multiple addresses in the destination subnet without configuring a specific helper-address for each destination. The answer to that question is "it depends". There is a function called directed broadcast which does exactly what the question wants, it forwards through the network and at the destination subnet it becomes a local broadcast. In old versions of IOS it was enabled by default. In current versions of IOS it is disabled by default (because of the potential of misuse in DOS attacks). If directed broadcast is enabled on the interface at the destination subnet then a configuration such as ip helper address 172.16.1.255 would send a broadcast to every station in the 172.16.1 subnet. If directed broadcast is not enabled at the destination interface then it will not work. (If helper address were configured for a directed broadcast and it is not enabled at the destination interface, then helper address would generate the packet, the packet would be forwarded to the destination, and the destination interface would discard the packet)
HTH
Rick
