Cisco advises using UDP as the outgoing transport only when connecting to systems or applications that do not support TCP.
Checked 2026-10-02
- Vendor
- Cisco
- Product
- Unified Communications Manager
- Subsystem
- SIP Trunk Security Profile
- Deployment
- on-premises
- Region
- not restricted
- Release range
- Release 15 and SUs
- Checked
- 2026-10-02
Sources
- Security Guide for Cisco Unified Communications Manager, Release 15 and SUs - Trunk and Gateway SIP Security — Cisco Systems · tier 2 current vendor documentation · SIP Trunk Security Profile Settings > Outgoing Transport Type
Cite this note
APA
WarmTransfer. (2026, October 2). Troubleshooting Unified CM SIP trunks that show No Service: source note cucm-sip-trunk-no-service-troubleshooting-udp-only-if-needed. WarmTransfer. https://warmtransfer.net/knowledge/claims/cucm-sip-trunk-no-service-troubleshooting-udp-only-if-needed
BibTeX
@misc{warmtransfer-claim-cucm-sip-trunk-no-service-troubleshooting-udp-only-if-needed,
title = {Troubleshooting Unified CM SIP trunks that show No Service: source note cucm-sip-trunk-no-service-troubleshooting-udp-only-if-needed},
author = {{WarmTransfer}},
year = {2026},
url = {https://warmtransfer.net/knowledge/claims/cucm-sip-trunk-no-service-troubleshooting-udp-only-if-needed},
note = {Source note cucm-sip-trunk-no-service-troubleshooting-udp-only-if-needed, checked 2026-10-02}
}