Source note · Troubleshooting calls that drop on hold or transfer
A REFER from Microsoft can arrive from any Microsoft signalling IP address on a new TLS connection, even if the earlier part of the call came from a different address, so firewall and SBC rules must allow all Microsoft signalling addresses.
Checked 2026-09-30
- Vendor
- Microsoft
- Product
- Teams Phone Direct Routing
- Subsystem
- call-transfer
- Deployment
- multi-tenant
- Region
- not restricted
- Release range
- current as of 2026-09-30
- Checked
- 2026-09-30
Sources
- Issues with call transfers - Microsoft Teams — Microsoft · tier 2 current vendor documentation · No SIP REFER received by the SBC from the SIP proxy, step 2
Cite this note
APA
WarmTransfer. (2026, September 30). Troubleshooting calls that drop on hold or transfer: source note sip-reinvite-call-drops-dr-refer-any-ip. WarmTransfer. https://warmtransfer.net/knowledge/claims/sip-reinvite-call-drops-dr-refer-any-ip
BibTeX
@misc{warmtransfer-claim-sip-reinvite-call-drops-dr-refer-any-ip,
title = {Troubleshooting calls that drop on hold or transfer: source note sip-reinvite-call-drops-dr-refer-any-ip},
author = {{WarmTransfer}},
year = {2026},
url = {https://warmtransfer.net/knowledge/claims/sip-reinvite-call-drops-dr-refer-any-ip},
note = {Source note sip-reinvite-call-drops-dr-refer-any-ip, checked 2026-09-30}
}