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New Member

Multicast MoH to remote branch office

Hi there,

We have a configuration in our labs as follows:

CCM Cluster with MoH --> 3550 SMI --> 4000 router --> DCE --> Frame Relay --> DTE --> 2600 router --> 4500 switch --> IP phones

We want to use multicast MoH to the phones in the remote branch (off the 4500 switch). MoH is configured on one CCM with multicast address 239.1.1.1 and all router interfaces between the MoH server and IP phones have been enabled with PIM sparse-dense mode. The 2600 router does contain an entry for 239.1.1.1 after issuing the 'show ip mroute' command:

(*, 239.1.1.1), 2d10h/stopped, RP 0.0.0.0, flags: D

Incoming interface: Null, RPF nbr 0.0.0.0

Outgoing interface list:

Serial0/0.1, Forward/Sparse-Dense, 2d10h/00:00:00

([MoH server IP address], 239.1.1.1), 00:01:16/00:01:43, flags: PT

Incoming interface: Serial0/0.1, RPF nbr [4000 router IP address]

Outgoing interface list: Null

However, when a phone is put on hold, we simply hear the beep sound at regular intervals, not any music.

It looks like the 2600 router does not seem to join the Ethernet interface (connected to the 4500 switch with the IP phones) to the MoH multicast group. The question is, why is this so? The 4500 switch is not doing anything at Layer 3, so multicast routing and PIM are not enabled. Could this be the issue? I wouldn't think so since the multicast stream is getting past the 3550 switch which also isn't configured for multicast routing and PIM.

Any thoughts would be much appreciated. I believe that the CCM configuration itself (with regards to MoH and resource groups etc.) is correct.

Regards,

Evan

6 REPLIES
Blue

Re: Multicast MoH to remote branch office

Evan,

Check your MOH server configuration in Call Manager to make sure that the max hops is greater than the default 2. This will prevent you from getting past the 1st router.

If that doesn't do the trick, configure the router closest to the MOH source as a Rendevous Point (RP). I have had better luck with static RP config as opposed to the auto RP setup.

Have Fun!

Dave

New Member

Re: Multicast MoH to remote branch office

Hi Dave,

Thanks for your post. However, as mentioned, I believe (I could be wrong!) the configuration on the CCM is correct. With regards to the max hops, I had set it to 15 on the CCM to make sure it got as far as possible.

I still think it may be the 4500 switch. The switch itself has two SVI defined....one VLAN for voice and one for data. But it does no routing (ie. no IP address on the SVI). As such, there is a question whether it is behaving as a switch or router. I'm wondering if I have to enable PIM on the voice SVI of the 4500 switch.

Cheers,

Evan

Blue

Re: Multicast MoH to remote branch office

Evan,

Put one of the 4500 connected phones on hold and do a "show ip igmp group" on your 2600. If you are not seeing the phone request to join the 239 stream then you will know that the request is not making it through the 4500.

If it is joining then an sh ip mroute on both routers should show you where it is being pruned.

I have not played with a 4500, but a quick look at the docs shows it will do it all. You need it to do IGMP snooping, and you will need the interface on the 2600 configured for IP pim sparse-dense. Most switches running IGMP will autodiscover a multicast router port, but there will be a show command that will verify this.

Dave

Gold

Re: Multicast MoH to remote branch office

If you're getting "tone on hold", it's because for whatever reason, CCM has determined there's not a valid MOH source available for that device. If CCM had decided you were eligible for a particular multicast MOH stream but you had some sort of defect in your multicast configuration, the user would hear complete silence rather than tone-on-hold.

Completely re-verify that your Media Resource Groups and Group LIsts contain the proper multicast-capable MOH servers, are applied to the right devices or device pools, the MOH servers are set to multicast-capable, the MRG is configured to use multicast, etc etc. Temporarily configure the device to receive a unicast MOH source instead to test out your MRG/MRGL/Device Pool configuration.

Verify that at least one MOH server is registered _to the same CallManager_ as the device that needs to receive MOH streams. Cisco advertises that MOH sources are shared across a cluster, but in this very forum, at least one Cisco employee has stated that you can only draw a MOH stream from a MOH server registered with the same CallManager you are registered to (sorry, I can't think of the name/link right now).

Blue

Re: Multicast MoH to remote branch office

Jason,

You are exactly right, he would just get silence if it was a multicast issue.

I have a 3.3.2 spB cluster with multiple subscribers, and no problem with MOH from my single MOH server to phones registered to different subs. Perhaps this was an issue with earlier releases?

Dave

Gold

Re: Multicast MoH to remote branch office

This may be true; I can't attest for that one way or the other. Almost all of our installations are two-CCM pub/sub installations where the pub has no devices registered unless the sub has failed, so I haven't really tested that theory out.

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