3Com Router 3000 Ethernet FamilyConfiguration Guide Chapter 7 Multicast Static Route Configuration3Com Corporation7-1Chapter 7 Multicast Static Route Configuration7.1 Multicast Static Route OverviewA multicast network topology may be different from a unicast topology. Some routers inthe network may only support unicast rather than multicast. Multicast static routes arehelpful when you need to separate paths between unicast datagram and multicastdatagram.For example, when there are routers not supporting multicast on the path between thesource and the destination, a multicast router can use a tunnel to transmit multicastpackets to a neighboring multicast router. As shown in Figure 7-1, each unicast routersupports unicast only. Multicast datagram transmits between multicast routers over atunnel. If no multicast static route is configured, unicast datagram will also be sent overthe tunnel. When a multicast static route is configured, the tunnel is specialized inmulticast datagram transmission.Multicast Unicast MulticastTunnelUnicastUnicastUnicastMulticast Unicast MulticastTunnelUnicastUnicastUnicastFigure 7-1 Transmit a multicast datagram over a tunnelMulticast static routes only have effect on the related multicast routers and will not beadvertised or imported to any other router in any way.7.2 Multicast Static Route ConfigurationMulticast Static Route configuration tasks include:z Configure a multicast static routez Change the multicast RPF route selection policyNote:Multiple multicast static routes on a same network segment are matched by order ofconfiguration. It is therefore very important to ensure the correct configurationsequence.
