Multicast

From: gladston@br.ibm.com
Date: Thu Jun 30 2005 - 18:22:25 GMT-3


source-------R2--tunnel---R3-------receiverA
              \ /
               \ /
                \ /
                 \ /
                    R5
                     \
                      \
                       receiverB

R5 is the hub, connected via serial 0 to R2 and R3.
Tunnel between R2 and R3 solves the problem of R3 receiving multicast from source (it would not receive via R5)
When a receiver joines R5, it send a join via s0. R2 and R3 receives it. R5 can not prune one of
the routers (R3 or R2), because it is a common serial (s0), and both routers would receive the prune.
So, R5 receives duplicate packets.

Would you have a solution for duplicate packets on R5?

For me it seems to be a limitation and it would be required a topology change.

Rack2R2#sh ip mroute 239.2.2.2

(148.5.46.1, 239.2.2.2), 00:11:53/00:02:56, flags: T
  Incoming interface: Ethernet0/0, RPF nbr 148.5.26.6, Mroute
  Outgoing interface list:
    Tunnel23, Forward/Sparse-Dense, 00:10:06/00:00:00
    Serial0/0.235, Forward/Sparse-Dense, 00:07:39/00:00:00

Rack2R3#sh ip mroute 239.2.2.2

(148.5.46.1, 239.2.2.2), 00:09:36/00:02:50, flags: T
  Incoming interface: Tunnel23, RPF nbr 148.5.2.1, Mroute
  Outgoing interface list:
    Ethernet0/0, Forward/Sparse-Dense, 00:09:37/00:00:00
    Serial1/0.235, Forward/Sparse-Dense, 00:09:37/00:00:00



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