Source note · SIP 503 and trunk out-of-service failures
For DNS SRV destinations, if CUBE gets a 503 or no response to an INVITE it marks that destination busyout and tries the next destination; the call is rejected if all destinations are busied out.
Checked 2026-09-25
If CUBE receives a 503 response or no response for the INVITE, CUBE then marks that destination as busyout
- Vendor
- Cisco
- Product
- CUBE
- Subsystem
- SIP trunk monitoring
- Deployment
- on-premises
- Region
- not restricted
- Release range
- IOS XE 17.6 onwards
- Checked
- 2026-09-25
Sources
- Cisco Unified Border Element Configuration Guide - Cisco IOS XE 17.6 Onwards - SIP Trunk Monitoring — Cisco · tier 2 current vendor documentation · SIP Trunk Monitoring chapter, subsection 'OPTIONS Ping for DNS SRV Hosts'
Cite this note
APA
WarmTransfer. (2026, September 25). SIP 503 and trunk out-of-service failures: source note sip-503-trunk-failures-cube-invite-503-next. WarmTransfer. https://warmtransfer.net/knowledge/claims/sip-503-trunk-failures-cube-invite-503-next
BibTeX
@misc{warmtransfer-claim-sip-503-trunk-failures-cube-invite-503-next,
title = {SIP 503 and trunk out-of-service failures: source note sip-503-trunk-failures-cube-invite-503-next},
author = {{WarmTransfer}},
year = {2026},
url = {https://warmtransfer.net/knowledge/claims/sip-503-trunk-failures-cube-invite-503-next},
note = {Source note sip-503-trunk-failures-cube-invite-503-next, checked 2026-09-25}
}