Appendix B: Integrating Cisco Unified Communications Manager and Cisco Unified SRST to Use Cisco Unified SRST
Information About Using Cisco Unified SRST Gateways as a Multicast MOH Resource
287
Cisco Unified SCCP and SIP SRST System Administrator Guide
OL-13143-04
MOH from Flash Files
The MOH Multicast from Flash Files feature facilitates the continuous multicast of MOH audio feed
from files in the flash memories of Cisco Unified SRST branch office routers during Cisco Unified
Communications fallback and normal Cisco Unified Communications service. Multicasting MOH from
individual branch routers saves WAN bandwidth by eliminating the need to stream MOH audio from
central offices to remote branches.
The MOH Multicast from Flash Files feature can act as a backup mechanism to the MOH live feed
feature. Using the Flash to backup the live-feed is the recommend method rather than using just the live
feed feature alone.
Cisco Unified Communications Manager MOH audio files must reach the WAN and another set must
not. Audio packets from the central Cisco Unified CM must cross the WAN to reach branches running
Cisco Unified CM. For branches running Cisco Unified SRST, the packets must not reach the WAN.
Table 1
provides a summary of options for MOH.
Table 1
Music-on-Hold (MOH)
Audio Source
Description
How to Configure
Flash memory
No external audio input is required.
Configuring Cisco Unified SRST for
Multicast MOH from an Audio File,
page 296
Live feed
The multicast audio stream has minimal
delay for local IP phones. The MOH
stream for PSTN callers is delayed by a
few seconds. If the live feed audio input
fails, callers on hold hear silence.
Configuring Cisco Unified SRST for
MOH from a Live Feed, page 306
Live feed and flash
memory
The live feed stream has a few seconds
of delay for both PSTN and local IP
phone callers. The flash MOH acts as
backup for the live-feed MoH.
We recommend this option if you want
live-feed because it provides guaranteed
MOH if the live-feed input is not found
or fails.
Configuring Cisco Unified SRST for
Multicast MOH from an Audio File,
page 296
and
Configuring Cisco Unified SRST for
MOH from a Live Feed, page 306