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Community Member

Multicast MoH redundancy

I have successfully configured Multicast MoH for a remote branch's IP phone. A router is used to stream the audio file to the remote branch. However, on that router, we can only specify 1 multicast group address with udp ports.

My question is what happen if the CCM1 at the central sites fail and the branch router register with another CCM2 in the same cluster, but this time the multicast address specified in this CCM2 server is different from CCM1 (i tried to put both address to be the same, but has an error). If the address is different, then the remote branch ip phone will listen to the different multicast group address and multicast MoH will fail...

Can anyone advise how can i achieve redundancy in multicast MoH scenario ?


Eng Wee


Re: Multicast MoH redundancy


you will have to use a different range of ip address for the multicast streams coming in from CCM2.

If CCM1 has start address of (increment by ip address), then the following ip addresses will be used for multicast streams from CCM1. - g711ulaw - g729a - g711alaw - wideband

So I would start using the following for CCM2 - g711ulaw - g729a - g711alaw - wideband



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Community Member

Re: Multicast MoH redundancy

Hi Sankar,

But the remote gateway router is only streaming 1 multicast address, say port 16384. So when CCM1 fail, the phone will listen to, but the router is streaming, so it will not work.


Eng Wee


Re: Multicast MoH redundancy

As you realized, this is a restriction with steaming Multicast MoH from the router.

As per this link, Only a single Cisco CallManager audio source can be used throughout the network

As a workaround, you can setup another router at the remote site to stream the multicast address of CCM2 server.



Community Member

Re: Multicast MoH redundancy

Hi Anup,

Thanks for your reply. We have dual router at the remote sites. Your suggestion will take care of CCM failure. But if one of the gateway routers at remote branch fail, the phone will still try to join the multicast group of gateway 1 (since the CCM is still working) which is no longer available.

So there is still a single point of failure.

Pls let me know if u have any other ideas.


Eng Wee

Re: Multicast MoH redundancy


I think you are pretty much limited here as only one stream can be sent from one router's flash at any time.

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