IP Multicast Helper Example

joiner

Figure 71
illustrates how a helper address on two routers converts from broadcast to multicast and back to broadcast.
Figure 71 IP Multicast Helper Scenario

The configuration on the first hop router converts a broadcast stream arriving at incoming Ethernet interface 0 destined for UDP port 4000 to a multicast stream. The access list denies other traffic from being forwarded into the multicast cloud. The traffic is sent to group address 224.5.5.5. Because fast switching does not perform such a conversion, the ip forward-protocol global configuration command causes the proper process level to perform the conversion.
The second configuration on the last hop router converts the multicast stream at incoming Ethernet interface 1 back to broadcast. Again, all multicast traffic emerging from the multicast cloud should not be converted to broadcast, only the traffic destined for UDP port 4000.
The configurations for Router A and Router C are as follows:
Router A—First Hop Router Configuration
interface ethernet 0
ip directed-broadcast
ip multicast helper-map broadcast 224.5.5.5 120
ip pim dense-mode
!
access-list 120 permit udp any any 4000
access-list 120 deny udp any any
ip forward-protocol udp 4000
Router C—Last Hop Router Configuration
interface ethernet 1
ip directed-broadcast
ip multicast helper-map 224.5.5.5 178.21.34.255 135
ip pim dense-mode
!
access-list 135 permit udp any any 4000
access-list 135 deny udp any any
ip forward-protocol udp 4000


本文来自ChinaUnix博客，如果查看原文请点：http://blog.chinaunix.net/u/5101/showart_39423.html