Source note · SIP 503 and trunk out-of-service failures
Whether a 503 in reply to an OPTIONS keepalive takes a trunk down depends on the platform: Unified CM documents it as out of service, AudioCodes makes it configurable, and Teams Direct Routing health depends on whether the SBC keeps sending OPTIONS rather than on the response code.
inferred · Checked 2026-09-25
- Vendor
- multi-vendor
- Product
- SIP trunk keepalive
- Subsystem
- OPTIONS keepalive
- Deployment
- on-premises, multi-tenant
- Region
- not restricted
- Release range
- current as of 2026-09-25
- Status
- inferred
- Checked
- 2026-09-25
Sources
- Cisco Unified Communications Manager Trunks (Session Management Edition deployment guide 8.6(1)) — Cisco · tier 2 current vendor documentation · Synthesis of cisco-sme-861-trunks 'SIP OPTIONS Ping', audiocodes-sbc-um-740-proxy-sets 'Keep-Alive Failure Responses', ms-learn-dr-monitor SIP options section
Cite this note
APA
WarmTransfer. (2026, September 25). SIP 503 and trunk out-of-service failures: source note sip-503-trunk-failures-inf-options-503-varies. WarmTransfer. https://warmtransfer.net/knowledge/claims/sip-503-trunk-failures-inf-options-503-varies
BibTeX
@misc{warmtransfer-claim-sip-503-trunk-failures-inf-options-503-varies,
title = {SIP 503 and trunk out-of-service failures: source note sip-503-trunk-failures-inf-options-503-varies},
author = {{WarmTransfer}},
year = {2026},
url = {https://warmtransfer.net/knowledge/claims/sip-503-trunk-failures-inf-options-503-varies},
note = {Source note sip-503-trunk-failures-inf-options-503-varies, checked 2026-09-25}
}