You have a Microsoft Teams Phone deployment. You are deploying Direct Routing by using a certified Session Border ControNer CSBC). The FQDN of the SBC is sbc1.contoso.com. You use signaling port…

Question

Exhibit

Options

• AThe firewall blocks traffic on port 5067
• BLocation-Based Routing is enabled for the SBC.
• CCalling plan licenses are not assigned to users.
• DThe SIP options are disabled.

• A
  73% (33)
• B
  9% (4)
• C
  13% (6)
• D
  4% (2)

Explanation

Option A is correct because Direct Routing requires the SBC to communicate with Microsoft's SIP proxy over the configured signaling port - in this case, port 5067. If the firewall blocks that port in either direction, the SBC cannot establish a SIP trunk to Microsoft 365, which is exactly what the Teams admin center error reflects (typically a "TLS connectivity" or "SIP options not received" failure).

Why the distractors are wrong:

• B (Location-Based Routing): LBR restricts call routing based on network location but doesn't prevent calls outright or cause SBC connectivity errors in the admin center.
• C (Calling plan licenses): Direct Routing is specifically used instead of Microsoft Calling Plans, so Calling Plan licenses are irrelevant - users need Phone System licenses, not Calling Plan licenses.
• D (SIP options disabled): SIP OPTIONS is a heartbeat mechanism; disabling it may affect health monitoring but is not itself a cause of the firewall blocking traffic. The symptom described (error in admin center, no calls) points to a connectivity/transport-layer issue, not a SIP OPTIONS configuration setting.

Memory tip: Think "port = door." If the signaling port (5067 here, 5061 for default TLS) is blocked by a firewall, no SIP traffic can flow - it's like locking the front door of the SBC. Always verify firewall rules allow both inbound and outbound traffic on the configured signaling port between the SBC and Microsoft's IP ranges.

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