Source note · Troubleshooting fax over IP failures
In Cisco topologies that include Unified CM, the T.38 switchover first sends a T.38 offer with a 0.0.0.0 address and later another T.38 re-INVITE with the real IP address.
Checked 2026-10-02
- Vendor
- Cisco
- Product
- Cisco Unified Communications Manager
- Subsystem
- T.38 switchover
- Deployment
- on-premises
- Region
- not restricted
- Release range
- as documented 2015
- Checked
- 2026-10-02
Sources
- Fax-SIP Troubleshoot Guide — Cisco Systems · tier 2 current vendor documentation · T.38 re-INVITE SDP discussion, CUCM-involved topologies note
Cite this note
APA
WarmTransfer. (2026, October 2). Troubleshooting fax over IP failures: source note fax-over-ip-troubleshooting-cucm-zero-ip-reinvite. WarmTransfer. https://warmtransfer.net/knowledge/claims/fax-over-ip-troubleshooting-cucm-zero-ip-reinvite
BibTeX
@misc{warmtransfer-claim-fax-over-ip-troubleshooting-cucm-zero-ip-reinvite,
title = {Troubleshooting fax over IP failures: source note fax-over-ip-troubleshooting-cucm-zero-ip-reinvite},
author = {{WarmTransfer}},
year = {2026},
url = {https://warmtransfer.net/knowledge/claims/fax-over-ip-troubleshooting-cucm-zero-ip-reinvite},
note = {Source note fax-over-ip-troubleshooting-cucm-zero-ip-reinvite, checked 2026-10-02}
}