Configuring Ipv6 Multicast Routing And Forwarding; Overview; Rpf Check Mechanism - HP 6125XLG 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
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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
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the IPv6 multicast routing table are added to the IPv6 multicast forwarding table.

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
The basis for an RPF check is an IPv6 unicast route. An IPv6 unicast routing table contains the shortest
path to each destination subnet. When a router performs an RPF check, it looks up its IPv6 unicast routing
table and chooses an optimal route. The detailed process is as follows: The router looks up its IPv6
unicast routing table by using the IPv6 address of the packet source as the destination address and
automatically selects the optimal route as the RPF route. The outgoing interface in the corresponding
routing entry is the RPF interface and the next hop is the RPF neighbor. The router considers the path
along which the IPv6 multicast packet from the RPF neighbor arrived on the RPF interface to be 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, or 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."
RPF check implementation in IPv6 multicast
Implementing an RPF check on each received IPv6 multicast packet would heavily burden the router. The
use of an IPv6 multicast forwarding table is the solution to this issue. When the router creates an IPv6
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"Configuring IPv6