300-820 · Question #214
Refer to the exhibit. An administrator set up a B2B interop with a business partner running a Microsoft Lync environment and can successfully make outbound video calls to [email protected]…
The correct answer is B. _sipfederationtcp._tcp.ciscovoice.com. Microsoft Lync (and Skype for Business) uses the _sipfederationtcp._tcp SRV record to discover the federation endpoint for routing inbound federated SIP calls. When a Lync environment tries to route an inbound call to [email protected], it performs a DNS SRV lookup for…
Question
Refer to the exhibit. An administrator set up a B2B interop with a business partner running a Microsoft Lync environment and can successfully make outbound video calls to [email protected]. Inbound calls to [email protected], however, are failing. A quick SRV search returns the records in the exhibit. Which record must be modified to resolve this challenge?
Exhibit
Options
- A_h323ls._udp.ciscovoice.com
- B_sipfederationtcp._tcp.ciscovoice.com
- C_sips._tcp.ciscovoice.com
- D_collab-edge._tls.ciscovoice.com
How the community answered
(40 responses)- A13% (5)
- B80% (32)
- C3% (1)
- D5% (2)
Explanation
Microsoft Lync (and Skype for Business) uses the _sipfederationtcp._tcp SRV record to discover the federation endpoint for routing inbound federated SIP calls. When a Lync environment tries to route an inbound call to [email protected], it performs a DNS SRV lookup for _sipfederationtcp._tcp.ciscovoice.com to find the Expressway-E or SIP endpoint that handles federation. If this record is missing, misconfigured, or pointing to the wrong address/port, inbound calls from the Microsoft environment will fail even when outbound calls succeed. The other records serve different purposes (H.323 gatekeeper, SIPS/TLS SIP, and MRA edge discovery).
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