Figure 17: Packet Flow Without Hardware Multicast Packet Replication - Juniper JUNOSE 11.0.X MULTICAST ROUTING Configuration Manual

Chapter 5: Configuring IPv6 Multicast
The bandwidth between the line module and the I/O module or IOA on the E Series
router is limited. A high-density Ethernet module provides eight physical ports that
can consume the bandwidth between the line module and the I/O module or IOA
before providing enough traffic to support egress line rate for all of these ports.
Figure 17 on page 161 displays how multicast traffic is typically replicated on the line
module. Each of these replicated packets is transmitted from the line module to the
I/O module or IOA.

Figure 17: Packet Flow Without Hardware Multicast Packet Replication

The hardware multicast packet replication feature enables you to configure multicast
traffic for a VLAN or S-VLAN to be replicated on the I/O module or IOA so that only
one copy of the packet is transmitted from the line module to the I/O module or IOA.
Replication for each of the ports is performed on the I/O module or IOA.
Configuring hardware multicast packet replication for high-density Ethernet is useful
when you want to provide the same multicast stream out of some or all of the ports,
such as for IP television (IPTV). Configuring hardware multicast packet replication
enables you to:
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Configuring Hardware Multicast Packet Replication