Pim Sparse-Dense Mode; Pim Source-Specific Multicast - Juniper JUNOSE 11.2.X MULTICAST ROUTING Configuration Manual

PIM Sparse-Dense Mode

PIM Source-Specific Multicast

Copyright © 2010, Juniper Networks, Inc.
NOTE: A PIM router can receive group-to-RP mappings from either BSR or auto-RP,
but not from both. Because BSR and auto-RP use different mapping algorithms, the
mechanisms cannot coexist.
NOTE: Static-override is configured using the override switch in the ip pim rp-address
command.
CAUTION: The maps distributed by BSR and Auto-RP for the same RP announcements
may be different. Because the Auto-RP mapping agent resolves mapping conflicts, a
PIM router that applies the BSR mapping algorithm to an Auto-RP distributed map
should produce the same result as a router that applies the Auto-RP mapping algorithm.
However, the reverse is not true. A PIM router that applies the BSR mapping algorithm
to a BSR distributed map may produce a different result to a router that applies the
Auto-RP mapping algorithm. This means that a PIM IPv4 domain can operate either
BSR or Auto-RP.
In PIM sparse-dense mode, if an RP is not known for a group, the router sends data using
PIM dense mode. However, if the router discovers an RP or you configure an RP statically,
PIM sparse mode takes over.
You can configure both PIM dense mode and PIM sparse mode commands in PIM
sparse-dense mode.
PIM SSM is an extension of the PIM protocol. Using SSM, a client can receive multicast
traffic directly from the source. PIM SSM uses PIM sparse mode functionality to create
an SPT between the client and the source, but builds the SPT without using an RP.
By default, the SSM group multicast address is limited to the IP address range 232.0.0.0
to 232.255.255.255. You can use the ip pim ssm command to extend SSM operations
into another Class D range. (See "Configuring PIM SSM" on page 103.)
An SSM-configured network has the following advantages over a traditionally configured
PIM sparse mode network include the following:
No need for shared trees or RP mapping (no RP is required).
No need for RP-to-RP source discovery through Multicast Source Discovery Protocol
(MSDP).
Chapter 3: Configuring PIM for IPv4 Multicast
83