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Configuring IPv6 PIM
This chapter describes IPv6 PIM, how to configure IPv6 PIM, configuration examples, and
troubleshooting methods.
Overview
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, IS-ISv6, or
BGP4+. IPv6 PIM uses an IPv6 unicast routing table to perform 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 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 modes:
•
Protocol Independent Multicast–Dense Mode for IPv6 (IPv6 PIM-DM)
•
Protocol Independent Multicast–Sparse Mode for IPv6 (IPv6 PIM-SM)
•
Bidirectional Protocol Independent Multicast for IPv6 (IPv6 BIDIR-PIM)
•
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 "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—LAN Switching Configuration Guide
).
IPv6 PIM-DM
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 following describes the basic implementation of IPv6 PIM-DM:
•
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.
Pruned branches resume IPv6 multicast forwarding when the pruned state times out. Data is
flooded again down these branches, and then the branches are pruned again.
•
The graft mechanism is used to reduce the latency for resuming the forwarding capability of a
previously pruned 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 the
SPT.
The operating mechanism of IPv6 PIM-DM is summarized as follows:
•
