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.