3Com 4007, Implementation Manual, Page: 427 / 684

How a Network Supports IP Multicast 427
Supporting Protocols in Your Module
To communicate with other routers, Switch 4007 Multilayer Switching
Modules support the Distance-Vector Multicast Routing Protocol
(DVMRP) version 3.6. DVMRP functions and configuration options are
explained later in this chapter.
To communicate with group members on directly attached subnetworks,
Switch 4007 Multilayer Switching Modules support the Internet Group
Management Protocol (IGMP) version 1 and version 2. IGMP functions are
covered later in this chapter.
IP Multicast Tunnels IP multicast routers are key connection points for delivering IP multicast
traffic between sources and multicast group members. In the event that
some routers in your network only transmit unicast packets, you can
configure a transitional technique called
tunneling to extend the service
area. Tunnels provide a virtual point-to-point link between two multicast
routers, where the path between them includes one or more routers that
do not support multicast routing (unicast routers).
Figure 51 DVMRP Tunnel Example
Figure 51 depicts a network configuration that requires an tunnel in order
for the PC to receive the IP multicast application. The multicast routers
support DVMRP, thus the tunnel is also configured with that protocol.
L3
L2
L3
L2
LAN
MAN
WAN
IP multicast
router
Unicast
router
Unicast
router
IP multicast
router
IP multicast
application source
IP multicast
group member
DVMRP tunnel
Switch Switch