Configuring Ipv6 Multicast Routing And Forwarding; Overview; Rpf Check Mechanism - HP 6125XLG Ip Multicast Configuration Manual

Configuring IPv6 multicast routing and
forwarding

Overview

IPv6 multicast routing and forwarding uses the following tables:
• IPv6 multicast protocols' routing tables, such as the IPv6 PIM routing table.
General IPv6 multicast routing table that summarizes the multicast routing information generated by
•
different IPv6 multicast routing protocols. The IPv6 multicast routing information from IPv6 multicast
sources to IPv6 multicast groups are stored in a set of (S, G) routing entries.
IPv6 multicast forwarding table that guides IPv6 multicast forwarding. The optimal routing entries in
•
the IPv6 multicast routing table are added to the IPv6 multicast forwarding table.
The term "interface" in this chapter collectively refers to Layer 3 interfaces, including VLAN interfaces
and Layer 3 Ethernet interfaces. You can set an Ethernet port as a Layer 3 interface by using the port
link-mode route command (see Layer 2

RPF check mechanism

An IPv6 multicast routing protocol relies on the existing IPv6 unicast routing information in creating IPv6
multicast routing entries. When creating IPv6 multicast routing table entries, an IPv6 multicast routing
protocol uses the reverse path forwarding (RPF) check mechanism to ensure IPv6 multicast data delivery
along the correct path. The RPF check mechanism also helps avoid data loops caused by various
reasons.
RPF check process
A router performs an RPF check based on its IPv6 unicast routing table. When performing the RPF check,
the router uses the packet's source IPv6 address as the destination address to look up the IPv6 unicast
routing table. It automatically selects an optimal route, of which the outgoing interface is the RPF interface
and the next hop is the RPF neighbor. If the RPF interface receives the IPv6 multicast packet from the RPF
neighbor, the router considers the path of the IPv6 multicast packet the shortest path that leads back to
the source.
The term "packet source" means different things in different situations:
For a packet that travels along the SPT from the multicast source to the receivers or the RP, the packet
•
source for RPF check is the multicast source.
For a packet that travels along the RPT from the RP to the receivers, the packet source for RPF check
•
is the RP.
For a packet that travels along the source-side RPT from the multicast source to the RP, the packet
•
source for RPF check is the RP.
For a bootstrap message from the BSR, the packet source for RPF check is the BSR.
•
For more information about the concepts of SPT, RPT, source-side RPT, RP, and BSR, see
PIM."
LAN Switching Configuration Guide).
—
253
"Configuring IPv6