In a 2009 3CX forum thread, incoming calls dropped at exactly 32 seconds and the logs said 'ACK is not received'. Removing a port-forwarding rule and correcting the public IP used in the Contact fixed most occurrences.

field report · Checked 2026-09-25

Vendor
3CX
Product
3CX Phone System
Subsystem
NAT / firewall
Deployment
on-premises
Region
not restricted
Release range
2009-era releases
Status
field report
Checked
2026-09-25

Sources

Cite this note

APA

WarmTransfer. (2026, September 25). Calls that drop after about 30 seconds: source note sip-calls-drop-30-seconds-3cx-32s-field-case. WarmTransfer. https://warmtransfer.net/knowledge/claims/sip-calls-drop-30-seconds-3cx-32s-field-case

BibTeX

@misc{warmtransfer-claim-sip-calls-drop-30-seconds-3cx-32s-field-case,
  title  = {Calls that drop after about 30 seconds: source note sip-calls-drop-30-seconds-3cx-32s-field-case},
  author = {{WarmTransfer}},
  year   = {2026},
  url    = {https://warmtransfer.net/knowledge/claims/sip-calls-drop-30-seconds-3cx-32s-field-case},
  note   = {Source note sip-calls-drop-30-seconds-3cx-32s-field-case, checked 2026-09-25}
}

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