CHAPTER 7. MultiCast Protocols
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Shared Trees
Shared trees or RP trees(RPT) rely on a central router called the Rendezvous
Point(RP) that receives all traffic from the sources, and forwards that traffic to
the receivers. All hosts might not be receivers. There is a single tree for each
multicast group, regardless of the number of sources. Only the routers on the
tree know about the group, and information is sent only to interested receivers.
With an RP, receivers have a place to join, even if no source exists.
The shared tree is unidirectional, and information flows only from the RP to
the receivers. If a host other than the RP has to send data on the tree, the data
must first be tunneled to the RP, and then multicast to the members.
This means that even if a receiver is also a source, it can only use the tree to
receive packets from the RP, and not to send packets to the RP(unless the
source is located between the RP and the receivers).
Bootstrap Router (BSR)
When a new multicast sender starts sending data packets, or a new receiver
starts sending the Join message towards the RP for that multicast group, it
needs to know the next-hop router towards the RP. The BSR provides group-
to-RP mapping information to all the PIM routers in a domain, allowing them
to map to the correct RP address.
IP Multicast Routing Table
Note:Multicast Routing Table displays of an RP router are different from other
routers.
The show ip mroute command displays the IP multicast routing table. In this
table: RPF nbr displays the unicast next-hop to reach RP. RPF idx displays the
incoming interface for this(*, G) state. RP displays the IP address for the RP
router.
The leading dots .... Stand for VIF index
Router_E# show ip pim sparse-mode mroute
IP Multicast Routing Table
(*,*,RP) Entries: 0
(*,G) Entries: 1
(S,G) Entries: 0
Summary of Contents for Ubigate iBG2016
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