Juniper JUNOSE 11.1.X MULTICAST ROUTING, Configuration Manual

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Configuring Hardware Multicast Packet Replication
You can configure IPv4 multicast to replicate packets to optimized hardware on a
logical port instead of using the forwarding controller (FC) on the router.
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 4 on page 18 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 4: 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
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Configuring Hardware Multicast Packet Replication
JUNOSe 11.1.x Multicast Routing Configuration Guide