3Com 4210, 5500G, 4200G manual Configuring PIM-SM plus Igmp plus Igmp Snooping

146CHAPTER 16: MULTICAST CONFIGURATION GUIDE

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vlan 1 to 3

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vlan 10 service-type multicast igmp-snooping enable

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interface Ethernet1/0/1 port link-type hybrid

port hybrid vlan 1 to 2 10 untagged port hybrid pvid vlan 2

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interface Ethernet1/0/2 port link-type hybrid

port hybrid vlan 1 3 10 untagged port hybrid pvid vlan 3

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interface Ethernet1/0/10 port link-type hybrid

port hybrid vlan 2 to 3 10 tagged port hybrid vlan 1 untagged

Precautions ■ A port belongs to one multicast VLAN only.

■Only Hybrid ports can be connected with receivers.

■Upon receiving a multicast packet, a router port forwards the packet only to the member ports in the same VLAN. Therefore, the member ports must belong to the same multicast VLAN with the router port.

■When assigning a router port to a multicast VLAN, be sure to configure it as a trunk port, or a hybrid port that sends packets of the multicast VLAN with the VLAN tag kept; otherwise all the member ports in this multicast VLAN will be unable to receive multicast packets.

Configuring PIM-SM plus IGMP plus IGMP Snooping

PIM-SM is a type of sparse mode multicast protocol. It uses the “pull mode” for multicast forwarding, and is suitable for large- and medium-sized networks with sparsely and widely distributed multicast group members.

The basic implementation of PIM-SM is as follows:

■PIM-SM assumes that hosts need multicast data only if they explicitly express their interest in the data. PIM-SM builds and maintains rendezvous point trees (RPT) for multicast traffic delivery. An RPT is rooted at a router in the PIM domain as the common node referred to as rendezvous point (RP), through which the multicast data travels along the RPT and reaches the receivers.

■When a receiver is interested in the multicast data addressed to a specific multicast group, the last-hop router sends a join message to the RP corresponding to that multicast group. The path along which the message goes hop by hop to the RP forms a branch of the RPT.

■When a multicast source sends multicast traffic to a multicast group, the first-hop router encapsulates the first packet in a register message, and sends the message to the corresponding RP by unicast. The arrival of this message at the RP triggers the establishment of an SPT rooted at the multicast source.