Lenovo Flex System Fabric CN4093, Инструкция по применению

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Chapter 31. Protocol Independent Multicast
Enterprise NOS supports Protocol Independent Multicast (PIM) in Sparse Mode
(PIM ‐ SM) and Dense Mode (PIM ‐ DM).
Note:
Enterprise NOS 8.4 does not support IPv6 for PIM.
The following sections discuss PIM support for the CN4093 10 Gb Converged
Scalable Switch:
 “PIM Overview” on page 497
 “Supported PIM Modes and Features” on page 498
 “Basic PIM Settings” on page 499
 “Additional Sparse Mode Settings” on page 502
 “Using PIM with Other Features” on page 504
 “PIM Configuration Examples” on page 505
PIM Overview
PIM is designed for efficiently routing multicast traffic across one or more IPv4
domains. This has benefits for application such as IP television, collaboration,
education, and software delivery, where a single source must deliver content (a
multicast) to a group of receivers that span both wide ‐ area and inter ‐ domain
networks.
Instead of sending a separate copy of content to each receiver, a multicast derives
efficiency by sending only a single copy of content toward its intended receivers.
This single copy only becomes duplicated when it reaches the target domain that
includes multiple receivers, or when it reaches a necessary bifurcation point
leading to different receiver domains.
PIM is used by multicast source stations, client receivers, and intermediary routers
and switches, to build and maintain efficient multicast routing trees. PIM is
protocol independent; It collects routing information using the existing unicast
routing functions underlying the IPv4 network, but does not rely on any particular
unicast protocol. For PIM to function, a Layer 3 routing protocol (such as BGP,
OSPF, RIP, or static routes) must first be configured on the switch.
PIM ‐ SM is a reverse ‐ path routing mechanism. Client receiver stations advertise
their willingness to join a multicast group. The local routing and switching devices
collect multicast routing information and forward the request toward the station
that will provide the multicast content. When the join requests reach the sending
station, the multicast data is sent toward the receivers, flowing in the opposite
direction of the original join requests.
Some routing and switching devices perform special PIM ‐ SM functions. Within
each receiver domain, one router is elected as the Designated Router (DR) for
handling multicasts for the domain. DRs forward information to a similar device,
the Rendezvous Point (RP), which holds the root tree for the particular multicast
group.