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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 105.)
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
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