Source note · SS7 and carrier interworking concepts
In the Cisco IOS 15M&T default SIP-to-PSTN mapping, SIP 503 Service Unavailable maps to cause 63 (service or option not available).
Checked 2026-09-24
- Vendor
- Cisco
- Product
- Cisco IOS voice gateway
- Subsystem
- cause code mapping
- Deployment
- on-premises
- Region
- not restricted
- Release range
- IOS 15M&T configuration guide updated 2014-11-25
- Checked
- 2026-09-24
Sources
- SIP Configuration Guide, Cisco IOS Release 15M&T - Configuring SIP Message Timer and Response Features — Cisco · tier 2 current vendor documentation · Section SIP - Configurable PSTN Cause Code Mapping, default SIP-to-PSTN table
Cite this note
APA
WarmTransfer. (2026, September 24). SS7 and carrier interworking concepts: source note ss7-carrier-interworking-cisco-sip503-cause63. WarmTransfer. https://warmtransfer.net/knowledge/claims/ss7-carrier-interworking-cisco-sip503-cause63
BibTeX
@misc{warmtransfer-claim-ss7-carrier-interworking-cisco-sip503-cause63,
title = {SS7 and carrier interworking concepts: source note ss7-carrier-interworking-cisco-sip503-cause63},
author = {{WarmTransfer}},
year = {2026},
url = {https://warmtransfer.net/knowledge/claims/ss7-carrier-interworking-cisco-sip503-cause63},
note = {Source note ss7-carrier-interworking-cisco-sip503-cause63, checked 2026-09-24}
}