Source note · SIP 503 and trunk out-of-service failures
With SIP OPTIONS Ping enabled, Unified CM considers a trunk destination out of service if it does not respond to OPTIONS, responds 503 or 408, or a TCP connection cannot be established.
Checked 2026-09-25
A destination address is considered to be 'out of service' if it fails to respond to an OPTIONS Request, if it sends a Service Unavailable (503) response or Request Timeout (408) response, or if a TCP connection cannot be established.
- Vendor
- Cisco
- Product
- Unified Communications Manager
- Subsystem
- SIP trunk OPTIONS ping
- Deployment
- on-premises
- Region
- not restricted
- Release range
- stated in the 8.6(1) SME design guide; later releases not verified from a fetched document
- Checked
- 2026-09-25
Sources
- Cisco Unified Communications Manager Trunks (Session Management Edition deployment guide 8.6(1)) — Cisco · tier 2 current vendor documentation · Subsection 'SIP OPTIONS Ping'
Cite this note
APA
WarmTransfer. (2026, September 25). SIP 503 and trunk out-of-service failures: source note sip-503-trunk-failures-cucm-oos-criteria. WarmTransfer. https://warmtransfer.net/knowledge/claims/sip-503-trunk-failures-cucm-oos-criteria
BibTeX
@misc{warmtransfer-claim-sip-503-trunk-failures-cucm-oos-criteria,
title = {SIP 503 and trunk out-of-service failures: source note sip-503-trunk-failures-cucm-oos-criteria},
author = {{WarmTransfer}},
year = {2026},
url = {https://warmtransfer.net/knowledge/claims/sip-503-trunk-failures-cucm-oos-criteria},
note = {Source note sip-503-trunk-failures-cucm-oos-criteria, checked 2026-09-25}
}