From: Pierre-Alex Guanel (paguanel@hotmail.com)
Date: Mon May 02 2005 - 10:11:13 GMT-3
Long,
"PIM-DM does not work over traditional NBMA networks unless a full mesh
topology
is used. Even when using a full mesh topology, the impact of pseudo
broadcast
makes pim-dm a poor choice for NBMA
networks."
From chapter 15: Developping IP multicast Networks
page 453 - 454
The reason NBMA network would not work if partially meshed is due to the
fact
that spoke do not "hear" about each other intentions to join or leave a
group:
if one of the spoke wants to leave a group
, it will prune the traffic at the hub and the other spoke - which may
still
need to use the multicast stream- will not know it should overide using a
joing
message because it did not "hear" the
prune.
IN SUMMURY: DON'T USE DENSE-MODE unless the network is FULLY MESHED
----------
As for using sparse-dense mode on the interface where you put ip
nbma-mode,
Cisco is very strong on the fact that you should not do it because this
mode
does not work well whith the ip nbma feature.
Use sparse mode only.
Hope this helps,
Pierre-Alex
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