[cisco-voip] Multicast MOH (MMOH) SRND Question

[Tim Smith]

This looks to be specific to re-broadcasting (which I haven’t had the pleasure of playing with yet)

Looking at the diagram in there. I assume you configure a new source with a multicast address on your MOH server.
If it’s set to re-broadcast, it’ll be looking to capture the input stream from that address.

Is it just saying since your MOH server is receiving MMOH on say 239.1.1.1:16384
(And would then re-broadcast this as Unicast where required)
It won’t send any multicast on that same address

But you can configure a multicast address – on that source – which means it re-broadcasts the original stream as multicast on a new multicast address as well.

MoH server for re-broadcasting + External Multicast source must be on same LAN (or at least have multicast routing connectivity between them) for the rebroadcasting – so if your server is receiving on one address, you wouldn’t want to be sending out on the same address.

That’s the way I read it which I think makes sense to me.

Cheers,

Tim

From: cisco-voip <cisco-voip-bounces at puck.nether.net> On Behalf Of Anthony Holloway
Sent: Thursday, 19 September 2019 1:00 AM
To: Cisco VoIP Group <cisco-voip at puck.nether.net>
Subject: [cisco-voip] Multicast MOH (MMOH) SRND Question

I was helping someone troubleshoot a MMOH issue and what was happening was that CUCM audio source, MOH Server, and MRG were all setup to do MMOH.  There was also a hardware MOH device on the network, which was sending MMOH on the same IP address (239.1.1.1) as the CUCM MOH Server.

When I pointed out that this would be a problem, I was shown the following statement from the SRND:

"If the multicast MoH server and the audio source are configured with the same multicast group address, when Phone B is placed on hold, it will receive the multicast RTP audio stream (E) from the original multicast stream (B) broadcast by the SRST router. In this case the MoH server does not send the audio because it is aware that the destination multicast IP address group is the same as the external audio source multicast stream (B) broadcast by the SRST router."

Source: https://www.cisco.com/c/en/us/td/docs/voice_ip_comm/cucm/srnd/collab11/collab11/media.html#pgfId-1393039

Now, a TAC case was opened, and TAC said it should have done what the SRND is stating, but I am doubtful.  I think the wording in the SRND is poor, and that perhaps it only pertains to the Fixed source of 51, and not just any source you create.

So, I'm asking for your understanding and knowledge of how this works, to clarify this aspect of MMOH for me.  Please read the entire section of the SRND linked, because context is important here.  I only provided a snippet.
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