Issue: Multicast and unicast MoH don’t work over the PSTN.
Platform: Cisco ISRs version 15.0.
Disable “IP CEF” in the router.
no ip cef
Cisco Express Forwarding is mainly used to increase packet switching speed thus disabling “IP CEF” is not recommended. Another workaround is to set Duplex Streaming Enabled to True under Service Parameter (Cisco CallManager).
If you are interested to know the details of this issue visit Cisco Bug Toolkit and locate this bug ID CSCtl21854.