Voice Port Configuration Guide, Cisco IOS Release 12.4T
Troubleshooting Analog and Digital Voice Port Configurations
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Troubleshooting Analog and Digital Voice Port Configurations

Troubleshooting Analog and Digital Voice Port Configurations

Last Updated: December 14, 2011

This chapter provides information to assist you in analyzing and troubleshooting voice port problems.

Troubleshooting Chart

The table below lists some problems that you might encounter after configuring voice ports. It also provides some suggested remedies.

Table 1 Troubleshooting Voice Port Configurations

Problem

Suggested Action

No connectivity

Ping the associated IP address to confirm connectivity. If you cannot successfully ping your destination, refer to the Cisco IOS IP Configuration Guide.

No connectivity

Enter the show controller t1 or show controller e1 command with the controller number for the voice port you are troubleshooting. This will tell you:

  • If the controller is up. If it is not, use the no shutdown command to make it active.
  • Whether alarms have been reported.
  • What parameter values have been set for the controller (framing, clock source, line code, cable length). If these values do not match those of the telephony connection you are making, reconfigure the controller.

See the "show controller Command: Examples" section in the "Verifying Analog and Digital Voice-Port Configurations" chapter for output.

No connectivity

Enter the show voice port command with the voice port number that you are troubleshooting, which will tell you:

  • If the voice port is up. If it is not, use the no shutdown command to make it active.
  • What parameter values have been set for the voice port, including default values (these do not appear in the output for the show running-config command). If these values do not match those of the telephony connection you are making, reconfigure the voice port.

See the "show voice port Command: Examples" section in the "Verifying Analog and Digital Voice-Port Configurations" chapter for sample output.

Telephony device buzzes or does not ring

Use the show voice port command to confirm that the ring frequency command is configured correctly. It must match the connected telephony equipment and may be country-dependent.

Distorted speech

Use the show voice port command to confirm the cptone keyword setting (also called region tone) is US.

Setting a wrong cptone could result in faulty voice reproduction during analog-to-digital or digital-to-analog conversions.

Music on hold is not heard

Reduce the configured level for the music-threshold command.

Background noise is not heard

Enable the comfort-noise command.

Long pauses occur in conversation; like speaking on a walkie-talkie

Overall delay is probably excessive; the standard for adequate voice quality is 150 milliseconds (ms) one-way transit delay. Measure delay by using ping tests at various times of the day with different network traffic loads. If delay must be reduced, areas to examine include propagation delay of signals between the sending and receiving endpoints, voice encoding delay, and the voice packetization time for various VoIP codecs.

Jerky or choppy speech

Variable delay, or jitter, is being introduced by congestion in the packet network. Two possible remedies are to:

  • Reduce the amount of congestion in your packet network. Pings between VoIP endpoints will give an idea of the round-trip delay of a link, which should never exceed 300 ms. Network queuing and dropped packets should also be examined.
  • Increase the size of the jitter buffer with the playout-delay command. (Refer to the Cisco IOS Voice Troubleshooting and Monitoring Guide.)

Clipped or fuzzy speech

  • Reduce input gain. (Refer to the Cisco IOS Voice Troubleshooting and Monitoring Guide.)
  • Change the voice activity detection (VAD) level. Sometimes VAD cuts the sound too early and the speaker's voice is clipped. You can also change the time that VAD waits for silence.

Clipped speech

Reduce the input level at the listener's router. (Refer to the Cisco IOS Voice Troubleshooting and Monitoring Guide.)

Volume too low or missed Dual-Tone Multifrequency (DTMF)

Increase speaker's output level or listener's input level. (Refer to the Cisco IOS Voice Troubleshooting and Monitoring Guide.)

Echo interval is greater than 25 ms (sounds like a separate voice)

Configure the echo-cancel enable command and increase the value for the echo-cancel coverage keyword. (See the "Configuring Echo Cancellation" section.)

Too much echo

Reduce the output level at the speaker's voice port. (Refer to the Cisco IOS Voice Troubleshooting and Monitoring Guide.)


Note


For information on test commands that force voice ports into specific states for testing refer to the Cisco IOS Voice Troubleshooting and Monitoring Guide.

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Any Internet Protocol (IP) addresses and phone numbers used in this document are not intended to be actual addresses and phone numbers. Any examples, command display output, network topology diagrams, and other figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses or phone numbers in illustrative content is unintentional and coincidental.

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