Source note · SIP ALG problems on firewalls and routers
If a device between a Direct Routing SBC and Microsoft could read and rewrite the Contact or Record-Route host to an IP address, Microsoft's documented rules would reject or fail the call. Because Direct Routing signaling runs over TLS, a firewall without TLS interception cannot normally rewrite it in the first place.
inferred · 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
- Status
- inferred
- Checked
- 2026-09-25
Sources
- Teams Phone System Direct Routing: SIP protocol — Microsoft · tier 2 current vendor documentation · Use of FQDN name in Contact or Record-Route; Contact header
Cite this note
APA
WarmTransfer. (2026, September 25). SIP ALG problems on firewalls and routers: source note sip-alg-problems-teams-dr-alg-rewrite-effect. WarmTransfer. https://warmtransfer.net/knowledge/claims/sip-alg-problems-teams-dr-alg-rewrite-effect
BibTeX
@misc{warmtransfer-claim-sip-alg-problems-teams-dr-alg-rewrite-effect,
title = {SIP ALG problems on firewalls and routers: source note sip-alg-problems-teams-dr-alg-rewrite-effect},
author = {{WarmTransfer}},
year = {2026},
url = {https://warmtransfer.net/knowledge/claims/sip-alg-problems-teams-dr-alg-rewrite-effect},
note = {Source note sip-alg-problems-teams-dr-alg-rewrite-effect, checked 2026-09-25}
}