Pim-Sm Receivers And Vlans - Avaya 8800 Planning And Engineering, Network Design

PIM-SM receivers and VLANs

Some designs cause unnecessarily traffic flow on links in a PIM-SM domain. In these cases, traffic
is not duplicated to the receivers, but waste bandwidth.
The following figure shows such a situation. Switch B is the Designated Router (DR) between
switches A and B. Switch C is the RP. A receiver R is placed on the VLAN (V1) that interconnects
switches A and B. A source sends multicast data to receiver R.
Figure 100: Receivers on interconnected VLANs
IGMP reports sent by R are forwarded to the DR, and both A and B create (*,G) records. Switch A
receives duplicate data through the path from C to A, and through the second path from C to B to A.
Switch A discards the data on the second path (assuming the upstream source is A to C).
To avoid this waste of resources, Avaya recommends that you do not place receivers on V1. This
guarantees that no traffic flows between B and A for receivers attached to A. In this case, the
existence of the receivers is only learned through PIM Join messages to the RP [for (*,G)] and of the
source through SPT Joins.
June 2016
Protocol Independent Multicast-Sparse Mode guidelines
Planning and Engineering — Network Design
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