Configuring Ipv6 Pim; Overview; Ipv6 Pim-Dm Overview - HP 6125G Configuration Manual

Configuring IPv6 PIM

Overview

Protocol Independent Multicast for IPv6 (IPv6 PIM) provides IPv6 multicast forwarding by leveraging IPv6
unicast static routes or IPv6 unicast routing tables generated by any IPv6 unicast routing protocol, such
as RIPng, OSPFv3, or BGP4+. IPv6 PIM uses an IPv6 unicast routing table to perform reverse path
forwarding (RPF) check to implement IPv6 multicast forwarding. Independent of the IPv6 unicast routing
protocols running on the device, IPv6 multicast routing can be implemented as long as the corresponding
IPv6 multicast routing entries are created through IPv6 unicast routes. IPv6 PIM uses the reverse path
forwarding (RPF) mechanism to implement IPv6 multicast forwarding. When an IPv6 multicast packet
arrives on an interface of the device, RPF check is performed on it. If the RPF check succeeds, the device
creates the corresponding routing entry and forwards the packet. If the RPF check fails, the device
discards the packet. For more information about RPF, see "Configuring IPv6 multicast routing and
forwarding."
Based on the implementation mechanism, IPv6 PIM supports the following types:
• Protocol Independent Multicast–Dense Mode for IPv6 (IPv6 PIM-DM)
Protocol Independent Multicast–Sparse Mode for IPv6 (IPv6 PIM-SM)
•
Protocol Independent Multicast Source-Specific Multicast for IPv6 (IPv6 PIM-SSM)
•
To facilitate description, a network comprising IPv6 PIM–supporting routers is referred to as an "IPv6 PIM
domain" in this document.
The term "router" in this document refers to both routers and Layer 3 switches.

IPv6 PIM-DM overview

IPv6 PIM-DM is a type of dense mode IPv6 multicast protocol. It uses the push mode for IPv6 multicast
forwarding, and is suitable for small-sized networks with densely distributed IPv6 multicast members.
The basic implementation of IPv6 PIM-DM is as follows:
IPv6 PIM-DM assumes that at least one IPv6 multicast group member exists on each subnet of a
•
network. Therefore, IPv6 multicast data is flooded to all nodes on the network. Then, branches
without IPv6 multicast forwarding are pruned from the forwarding tree, leaving only those branches
that contain receivers. This flood-and-prune process takes place periodically. That is, pruned
branches resume IPv6 multicast forwarding when the pruned state times out and then data is
flooded again down these branches, and then the branches are pruned again.
When a new receiver on a previously pruned branch joins an IPv6 multicast group, to reduce the
•
join latency, IPv6 PIM-DM uses the graft mechanism to resume IPv6 multicast data forwarding to
that branch.
In general, the IPv6 multicast forwarding path is a source tree. That is, it is a forwarding tree with the IPv6
multicast source as its "root" and IPv6 multicast group members as its "leaves." Because the source tree
is the shortest path from the IPv6 multicast source to the receivers, it is also called "shortest path tree
(SPT)."
The working mechanism of IPv6 PIM-DM is summarized as follows:
Neighbor discovery
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