Source note · Troubleshooting fax over IP failures

Which side sends the T.38 re-INVITE differs by carrier and direction (Bandwidth expects a customer re-INVITE; Telnyx defaults to sending it on outbound and expects the customer to send it on inbound), so a re-INVITE-side mismatch is a plausible cause of calls that never leave G.711.

inferred · Checked 2026-10-02

Vendor: not restricted
Product: not restricted
Subsystem: T.38 switchover
Deployment: multi-tenant
Region: not restricted
Release range: current as of 2026-10-02
Status: inferred
Checked: 2026-10-02

Sources

Fax service with Telnyx (via T.38 or G711) — Telnyx · tier 2 current vendor documentation · Outbound and inbound fax sections, read against bandwidth-support-t38-faxing-guide T.38 support section

Cite this note

APA

WarmTransfer. (2026, October 2). Troubleshooting fax over IP failures: source note fax-over-ip-troubleshooting-reinvite-side-varies. WarmTransfer. https://warmtransfer.net/knowledge/claims/fax-over-ip-troubleshooting-reinvite-side-varies

BibTeX

@misc{warmtransfer-claim-fax-over-ip-troubleshooting-reinvite-side-varies,
  title  = {Troubleshooting fax over IP failures: source note fax-over-ip-troubleshooting-reinvite-side-varies},
  author = {{WarmTransfer}},
  year   = {2026},
  url    = {https://warmtransfer.net/knowledge/claims/fax-over-ip-troubleshooting-reinvite-side-varies},
  note   = {Source note fax-over-ip-troubleshooting-reinvite-side-varies, checked 2026-10-02}
}

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