Streaming Multicast MOH (Music On Hold)

Music on hold – everyone takes for granted that their old digital PBX had a 3.5 mm Audio input jack for hooking up your mp3/music device for on hold music. While doing so might not be legal (its not), its considerably harder to do with a Cisco PBX as there isn’t much physical equipment left these days (except for course for your gateway devices). Server are VM’s now and while Cisco used to offer a USB based audio input device its long been forgotten and is no longer viable in the days of virtual appliances. So what are our options? We can use a multicast stream for our music on hold.  Not at all more complicated than that old audio input jack – but I digress. Here’s how to do it 🙂


  • Your Phones/gateway need to be on a separate sub-net from the CUCM. These devices need to be in separate vlan/subnets. This is a good idea regardless but is required in this configuration.
  • You’ll need the “Cisco IP Voice Media Streaming App” Service running on your CUCM server.

Step 1 – you’ll need a router, usually your PSTN gateway router is sufficient as it’ll already have voice DSP resources, hopefully enough to run an E&M card (VIC3-2E/M). The router will convert the audio input into this E&M port and create a multicast stream. If you don’t have resources available consider using a Cisco 2801/2811 router – these are very cheap second hand. I’m using a 2901 running 15.0(1r) in this example.

Step 2 – Create a  Multicast MOH Source within CUCM (be sure to enable Multicast on the CUCM registered MOH Server). Note that Hop count is reduced to 1, this will ensure multicast audio from CUCM will not reach the phones. Your CUCM server will also produce a silent audio stream on your chosen Multicast address, but your phones will only be able to hear the stream coming from your router.


MOH Audio Source

Step 3 – Configure your gateway

Gateway Items to setup. Keep in mind if you need Multicast to jump subnets you’ll need to PIM the Layer 3 interfaces.

You connect a line-level audio feed (standard audio source + – ) directly to pins 3 and 6 of an E&M RJ-45 connector. Custom make this cable, I haven’t come across any pre-made cables.

Config for the E&M Voice-port

Adjust the input gain on your E&M Port depending on how loud the MOH playback is on the phones.

voice-port 0/2/0
operation 4-wire
signal immediate
input gain 3

Setup the Dial-peer (random number)
dial-peer voice 7777 pots
destination-pattern 7777
port 0/2/0

Configure CME  to stream the audio source, multicast address and port should match was is used in your CUCM MOH Source.

ccm-manager music-on-hold
multicast moh port 16384 route
moh-live dn-number 3333 out-call 7777


And that’s it… Simple right? 🙂