Source note · SIP 503 and trunk out-of-service failures
In Direct Routing, the default SBC final response codes that trigger retry of an outbound call on another SBC in the voice route are 408, 503 and 504.
Checked 2026-09-25
Default values: 408, 503, 504
- Vendor
- Microsoft
- Product
- Teams Phone Direct Routing
- Subsystem
- outbound trunk failover
- Deployment
- multi-tenant
- Region
- not restricted
- Release range
- current as of 2026-09-25
- Checked
- 2026-09-25
Sources
- Trunk failover on outbound calls - Microsoft Teams — Microsoft · tier 2 current vendor documentation · Section 'Failover of specific SIP codes received from the Session Border Controller (SBC)', last line
Cite this note
APA
WarmTransfer. (2026, September 25). SIP 503 and trunk out-of-service failures: source note sip-503-trunk-failures-dr-failover-defaults. WarmTransfer. https://warmtransfer.net/knowledge/claims/sip-503-trunk-failures-dr-failover-defaults
BibTeX
@misc{warmtransfer-claim-sip-503-trunk-failures-dr-failover-defaults,
title = {SIP 503 and trunk out-of-service failures: source note sip-503-trunk-failures-dr-failover-defaults},
author = {{WarmTransfer}},
year = {2026},
url = {https://warmtransfer.net/knowledge/claims/sip-503-trunk-failures-dr-failover-defaults},
note = {Source note sip-503-trunk-failures-dr-failover-defaults, checked 2026-09-25}
}