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JunosE 11.3.x Multicast Routing Configuration Guide
PIM Sparse Mode Bootstrap Router
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When all designated routers associated with a specific RP router have switched to the
SPT, the RP router sends a join/prune message toward the multicast source. When the
multicast source receives this message, it stops sending multicast data through the SPT.
Joining Groups
A host's designated router (DR) sends join messages to the RP when that host wants to
join a group. When a host wants to leave a group, it communicates with its designated
router through IGMP. When the designated router no longer has any hosts that belong
to a particular group, it sends a prune message to the RP.
Timers
PIM sparse mode uses timers to maintain the networking trees.
NOTE: PIM sparse mode routers poll their neighbors and hosts for various
pieces of information at set intervals.
If a PIM sparse mode router does not receive information from a neighbor or host within
a specific time, known as the hold time, it removes the associated information from its
routing tables.
You can configure how often an interface sends hello messages (hello interval) and how
often routers send RP announce messages (RP announce interval). The hold-time
associated with hello messages is 3.5 times the hello interval, and the holdtime associated
with RP announce messages is 2.5 times the RP announce interval.
All other timers are fixed and take the default values recommended in RFC 2934—Protocol
Independent Multicast MIB for IPv4 (October 2000).
PIM sparse mode routers need the address of the rendezvous point (RP) for each group
for which they have (*,G) state. They obtain this address either through a bootstrap
mechanism or through static configuration. PIM sparse mode routers commonly use one
of two bootstrap mechanisms: bootstrap router (BSR) or auto-RP. Auto-RP is standards
based, but is not used in IPv6 implementations, so BSR configuration has become more
popular.
When implemented, BSR operates as follows:
One router in each PIM domain is elected the BSR.
1.
All the routers in the domain that are configured to be RP candidates periodically
2.
unicast their candidacy to the BSR.
The BSR picks an RP set from the available candidates and periodically announces
3.
this set in a bootstrap message.
Bootstrap messages are flooded hop by hop throughout the domain until all routers
4.
in the domain learn the RP set.
Copyright © 2010, Juniper Networks, Inc.
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