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Level 10
Level 10

Core Issue

There are several reasons for Cisco CallManager to play Tone on Hold (ToH) to an endpoint that has been configured for Music on Hold (MoH):

  • One reason is a mismatch between the codec configuration used by the MoH server and the region in which the endpoint is registered. For example, the MoH server advertised only a capability of G.711 mu-law. If an endpoint is in another region enforcing the G.729 codec, the Cisco CallManager chooses ToH because a stream cannot be played to this endpoint.

  • If location-based connection admission control is being used and there is no bandwidth available, then Cisco CallManager sends ToH rather than MoH.

  • If there are no available audio streams, it is because the MoH server has a finite number of unicast streams it can generate. Exceeding this limit causes Cisco CallManager to play ToH.


To resolve this issue, ensure that each of these issues are not causing ToH to be played and restart the IPVMS application service.

Refer the following document for more information

Problem Type

Call connection (Connection quality: One-way audio, no busy tone, dropped calls, etc.)

Call control software (CallManager, CallManager Express, ICS7750, SRST, SS7 call agents)

When Problem Occurs

While on hold

Music on Hold Device Counters in RTMT


Codec Type

Codec mismatch

Music on Hold (MoH)

Audio streams

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