Source note · Troubleshooting fax over IP failures
Cisco's 2013 CUBE third-party fax guidelines state that Verizon, although claiming T.38 over SIP support, never initiates a voice-to-T.38 switchover when it is the terminating gateway.
Checked 2026-10-02
- Vendor
- Cisco
- Product
- Cisco Unified Border Element
- Subsystem
- carrier interop
- Deployment
- on-premises
- Region
- us
- Release range
- as documented 2013-08-14
- Checked
- 2026-10-02
Sources
- CUBE Third-Party Interoperability Fax Guidelines — Cisco · tier 2 current vendor documentation · Verizon interoperability note within the T.38 configuration discussion
Cite this note
APA
WarmTransfer. (2026, October 2). Troubleshooting fax over IP failures: source note fax-over-ip-troubleshooting-verizon-no-tgw-switch. WarmTransfer. https://warmtransfer.net/knowledge/claims/fax-over-ip-troubleshooting-verizon-no-tgw-switch
BibTeX
@misc{warmtransfer-claim-fax-over-ip-troubleshooting-verizon-no-tgw-switch,
title = {Troubleshooting fax over IP failures: source note fax-over-ip-troubleshooting-verizon-no-tgw-switch},
author = {{WarmTransfer}},
year = {2026},
url = {https://warmtransfer.net/knowledge/claims/fax-over-ip-troubleshooting-verizon-no-tgw-switch},
note = {Source note fax-over-ip-troubleshooting-verizon-no-tgw-switch, checked 2026-10-02}
}