Helper-map for Broadcast to multicast conversion and vice versa.
The following is an example which illustrates the use of the helper-map command at the first-hop and the last-hop， to convert a broadcast stream directed to port 2000 to a multicast stream and back.
On the first hop router
-----------------------
The following example converts broadcast streams to port 2000 to a multicast stream（G = 224.5.5.5）
int < …… > /* incoming interface of broadcast stream */ ip multicast helper-map broadcast 224.5.5.5 101 ip pim dense……
ip forward-protocol udp 2000 access-list 101 permit udp any any eq 2000 access-list 101 deny udp any any
On the last hop router
---------------------
int <……> /* incoming interface of multicast stream */ ip multicast helper-map 224.5.5.5 178.21.34.255 101 ip pim dense……
ip forward-protocol udp 2000 access-list 101 permit udp any any eq 2000 access-list 101 deny udp any any
Note：o Configuring the multicast helper map command （to convert multicast to broadcast） will also automatically configure "ip igmp join-group " on the interface. The router must be joined to the multicast group to be translated to a broadcast address. o In Cisco IOS 12.0， it is necessary to configure the interface command "ip directed-broadcast" along with helper-map command. By default， it is turned off.
