Multicast Packet Forwarding Mechanism; Multicast Support For Vpns; Introduction To Vpn Instances - HP MSR2003 Configuration Manual

Multicast packet forwarding mechanism

In a multicast model, receiver hosts of a multicast group are usually located at different areas on the
network. They are identified by the same multicast group address. To deliver multicast packets to these
receivers, a multicast source encapsulates the multicast data in an IP packet with the multicast group
address as the destination address. Multicast routers on the forwarding paths forward multicast packets
that an incoming interface receives through multiple outgoing interfaces. Compared to a unicast model,
a multicast model is more complex in the following aspects:
To ensure multicast packet transmission in the network, different routing tables are used to guide
•
multicast forwarding. These routing tables include unicast routing tables, routing tables for multicast
(for example, the MBGP routing table), and static multicast routing tables.
• To process the same multicast information from different peers received on different interfaces of the
same device, the multicast device performs an RPF check on each multicast packet. The RPF check
result determines whether the packet will be forwarded or discarded. The RPF check mechanism is
the basis for most multicast routing protocols to implement multicast forwarding.
For more information about the RPF mechanism, see "Configuring multicast routing and
forwarding" and "Configuring IPv6 multicast routing and forwarding."

Multicast support for VPNs

Multicast support for VPNs refers to multicast applied in VPNs.

Introduction to VPN instances

VPNs must be isolated from one another and from the public network. As shown in
VPN B separately access the public network through PE devices.
Figure 9 VPN networking diagram
VPN B
CE b1
CE a1
VPN A
VPN A
CE b2
PE 1
Public network
CE a2
CE b3
PE 2
P
PE 3
11
Figure
VPN B
CE a3
VPN A
9, VPN A and