With multicast MOH and an ISR 4431 gateway, external callers on hold hear silence because the gateway discards MOH RTP that does not match the media address in signalling; the documented fix is to set the Cisco CallManager clusterwide service parameter Duplex Streaming Enabled to True, with no service restart required.
Checked 2026-09-30
- Vendor
- Cisco
- Product
- Unified Communications Manager
- Subsystem
- music-on-hold
- Deployment
- on-premises
- Region
- not restricted
- Release range
- CUCM 9.x and above with ISR 4431 on IOS XE
- Checked
- 2026-09-30
Sources
- Troubleshoot Music On Hold Failure When Gateway is Integrated Service Router 4431 — Cisco Systems · tier 2 current vendor documentation · sections 'Problem' and 'Solution'
Cite this note
APA
WarmTransfer. (2026, September 30). Troubleshooting Unified CM media resource allocation failures: source note cucm-media-resource-failures-moh-isr4431-duplex. WarmTransfer. https://warmtransfer.net/knowledge/claims/cucm-media-resource-failures-moh-isr4431-duplex
BibTeX
@misc{warmtransfer-claim-cucm-media-resource-failures-moh-isr4431-duplex,
title = {Troubleshooting Unified CM media resource allocation failures: source note cucm-media-resource-failures-moh-isr4431-duplex},
author = {{WarmTransfer}},
year = {2026},
url = {https://warmtransfer.net/knowledge/claims/cucm-media-resource-failures-moh-isr4431-duplex},
note = {Source note cucm-media-resource-failures-moh-isr4431-duplex, checked 2026-09-30}
}