Source note · SIP ALG problems on firewalls and routers
For Teams Direct Routing, every incoming OPTIONS and INVITE to the Microsoft SIP proxy must carry the paired SBC's FQDN, not an IP address, in the Contact header URI hostname.
Checked 2026-09-25
- Vendor
- Microsoft
- Product
- Teams Phone Direct Routing
- Subsystem
- SIP signaling
- Deployment
- multi-tenant, hybrid
- Region
- not restricted
- Release range
- current as of 2026-09-25
- Checked
- 2026-09-25
Sources
- Teams Phone System Direct Routing: SIP protocol — Microsoft · tier 2 current vendor documentation · Detailed requirements for Contact header and Request-URI > Contact header
Cite this note
APA
WarmTransfer. (2026, September 25). SIP ALG problems on firewalls and routers: source note sip-alg-problems-teams-dr-contact-fqdn. WarmTransfer. https://warmtransfer.net/knowledge/claims/sip-alg-problems-teams-dr-contact-fqdn
BibTeX
@misc{warmtransfer-claim-sip-alg-problems-teams-dr-contact-fqdn,
title = {SIP ALG problems on firewalls and routers: source note sip-alg-problems-teams-dr-contact-fqdn},
author = {{WarmTransfer}},
year = {2026},
url = {https://warmtransfer.net/knowledge/claims/sip-alg-problems-teams-dr-contact-fqdn},
note = {Source note sip-alg-problems-teams-dr-contact-fqdn, checked 2026-09-25}
}