Contents

• Telephony
• Call Dropped on TLS High-Availability System
• Call-Back Issues
• Call-In Issues
• Cannot Enter Meeting
• User Calls are Dropped After Failover
• Voice Activity Detection (VAD) Support Issues

Telephony

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This section includes telephony troubleshooting topics.

• Call Dropped on TLS High-Availability System
• Call-Back Issues
• Call-In Issues
• Cannot Enter Meeting
• User Calls are Dropped After Failover
• Voice Activity Detection (VAD) Support Issues

Call Dropped on TLS High-Availability System

Problem    In a large environment with configured for TLS (security encryption conferencing) conference calls might be dropped.

Possible Cause    Your network is disconnected between your primary and high-availability virtual machines for a few minutes while a meeting is taking place. The network then recovers while the meeting is still taking place.

Solution    Participants must manually rejoin their meeting.

Call-Back Issues

Problem    When you attempt to have the system call your phone number, the phone does not ring and you receive an error message: "Call back failed; no answer."

Possible Cause    You need to reconfigure your CUCM servers.

Solution    In CUCM, go to the SIP trunks configured for Cisco WebEx Meetings Server, and check the configured Calling Search Space. Go to your phone under Devices, and check the configured partition. Select Call Routing > Class of Control > Calling Search Space, go to the configured calling search space and make sure it has the partition listed configured for your phone.

Call-In Issues

Problem    Users hear a reorder tone before or after the complete number is dialed.

Problem    The "Your call cannot be completed as dialed" message is played by the annunciator.

Possible Cause    You need to reconfigure your CUCM servers.

Solution    In CUCM, go to the route pattern being used for Cisco WebEx Meetings Server, and check the configured partition. Then go to the device you are calling from and check the configured Calling Search Space. Select Call Routing > Class of Control > Calling Search Space, go to the configured calling search space and make sure it has the partition listed configured for the route pattern for Cisco WebEx Meetings Server. If the partition is set to <None> any device configured in Cisco Unified Communications Manager would be able to call Cisco WebEx Meetings Server.

Cannot Enter Meeting

Problem    During call-in, a user's call terminates or there is no sound after entering the meeting ID followed by #.

Problem    During call-back, a user's call terminates after entering 1 to join the meeting.

Possible Cause    You need to reconfigure your CUCM servers.

Solution    In CUCM, check your SIP route patterns configured for Cisco WebEx Meetings Server and check the configured route partition. Go to the SIP trunks configured for the load balancers and check the configured Rerouting Calling Search Space and Out-Of-Dialog Refer Calling Search Space. Select Call Routing > Class of Control > Calling Search Space, go to the configured Rerouting Calling Search Space and Out-Of-Dialog Refer Calling Search Space and make sure they each have the partition listed configured for the SIP Route Pattern for Cisco WebEx Meetings Server.

User Calls are Dropped After Failover

Problem    User calls are dropped after failover occurs on your high-availability system.

Possible Cause    Your system has TLS enabled and uses a KPML IP phone. TAS attempts to send a subscribe SIP message to Cisco Unified Communications Manager (CUCM). The subscribe message cannot pass CUCM validation due to the change in the TAS IP address. To configure your CUCM settings, sign into the Administration Site and select Settings > Audio and then find the CUCM fields.

Solution    This is a known issue and there are no configuration changes that can fix this problem at this time. When calls are dropped because of this problem, users must rejoin the meeting by dialing back in.

Voice Activity Detection (VAD) Support Issues

Problem    Cisco WebEx Meetings Server does not recognize the remote peer VAD enable/disable condition and disables the VAD parameter by default. VAD, also known as speech activity detection or speech detection, is a technique used in speech processing in which the presence or absence of human speech is detected.

Possible Cause    Cisco WebEx Meetings Server does not perform the SDP-based negotiation for VAD support. Starting from Cisco WebEx Meetings Server 1.1 MR2 and later, by default Cisco WebEx Meetings Server disables VAD. Earlier versions of Cisco WebEx Meetings Server enable VAD by default. By disabling VAD, the bandwidth consumed for the codec that is being used will not exceed the standard bandwidth requirements for that codec. For example, the bandwidth consumption for G.711 will be 64 kbps when VAD is disabled. VAD does not impact user experience in any way. When VAD is enabled, Cisco WebEx Meetings Server helps to save network bandwidth depending on the active speech detected. When there is silence, Cisco WebEx Meetings Server sends a special SID packet indicating the silence and stops sending packets which helps to save network bandwidth. It starts sending audio packets again when there is voice activity detected.

Solution    VAD negotiation through SDP is not currently supported by Cisco WebEx Meetings Server.