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Multicast Music on Hold in SRST

While in SRST, the IOS router can play an audio file from its flash as a multicast MOH to users in the remote sites (similar to multicast MOH explained in Chapter 6, “Cisco Collaboration Solution Bandwidth Management”). This feature has the following limitations:

  • A single MOH source should be used for all phones at remote sites. Multicast MOH can only support one file.
  • Cisco Unified SRST multicast MOH supports only G.711, and MOH from an SRST router cannot be unicast. Multicast MOH can work in one of the following two ways:

    • Nonfallback mode: This occurs when the WAN link is up and the phones are controlled by CUCM. It allows the phones to consult a local MOH file instead of reaching out to CUCM across the WAN. This option is covered in detail in Chapter 6.
    • Fallback mode: This occurs when SRST is active; i.e., the remote site has lost connectivity to the central-site CUCM. In this case, the branch router can continue to provide multicast MOH.

For configuring multicast MOH, CUCM and voice gateway at remote sites must be configured to support multicast. See multicast configuration for supporting MOH in Chapter 6. Assuming that multicast routing in the router is enabled and PIM dense mode is configured for identified interfaces, both CUCM and the IOS router need to be configured to support multicast MOH. To configure CUCM for supporting multicast MOH, follow these steps:

  • Step 1. Go to CUCM Administration GUI > Media Resources > Music on Hold Audio Source and select the audio source you are enabling for multicast. Ensure that the Allow Multi-casting check box is checked, as shown in Figure 5-6.

    Figure 5-6

    Figure 5-6 Multicast MOH Audio Source

  • Step 2. Go to Media Resources > Music on Hold Server Configuration. Enable multicast support and select the option between port number or IP address. Ensure that the MOH server has a G.711 only enabled device pool assigned to it.
  • Step 3. Go to Media Resources > Media Resource Group (MRG) and click Add New. Add a new MRG and ensure that this MRG has the multicast-enabled MOH server assigned to it and is multicast enabled, as shown in Figure 5-7.

    Figure 5-7

    Figure 5-7 Multicast-Enabled MRG

  • Step 4. Assign the MRG to an MRGL by going to Media Resources > Media Resource Group List and assign the MRGL to a device pool.

Example 5-5 outlines the configuration of an IOS SRST router.

Example 5-5 SRST Router Multicast Configuration

SRST-Router(config)# ccm-manager music-on-hold
!
SRST-Router(config)# interface loopback 1
SRST-Router(config-if)# ip address 10.86.108.82 255.255.255.255
!
SRST-Router(config)# call-manager-fallback
SRST-Router(config-cm-fallback)# ip source-address 10.76.108.78 port 2000
SRST-Router(config-cm-fallback)# moh music-on-hold.au
SRST-Router(config-cm-fallback)# multicast moh 239.1.1.1 port 16384 route 10.86.108.82 10.76.108.78
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