Cisco IOS Voice Troubleshooting and Monitoring -- Analog DID Interfaces

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Direct inward dialing (DID) is a service offered by telephone companies that enables callers to dial directly to an extension on a PBX without the assistance of an operator or automated call attendant. This service makes use of DID trunks, which forward only the last three to five digits of a phone number to the PBX. The DID state machine is identical to the E&M state machine.

Guide Contents
Troubleshooting Cisco IOS Voice Overview
Debug Command Output on Cisco IOS Voice Gateways
Filtering Troubleshooting Output
Cisco VoIP Internal Error Codes
Troubleshooting Cisco IOS Voice Telephony
Troubleshooting Cisco IOS Voice Protocols
Troubleshooting Cisco IOS Telephony Applications
Monitoring the Cisco IOS Voice Network
Cause Codes and Debug Values


DID Topology

Figure: DID Support for Cisco 2600 and Cisco 3600 Series Routers shows a hypothetical topology in which a user connected to the PSTN (User A) dials various numbers and is connected to the appropriate extensions on a PBX.

Figure: DID Support for Cisco 2600 and Cisco 3600 Series Routers


Number Dialed by User A Number Received by Router Extension Receiving Call



User C



User D



User B



No dial-peer match found; fast busy tone is played

DID Hardware Troubleshooting

A DID voice interface connects directly to a standard telephone, fax machine, or similar device and supplies ring, voltage, and dial tone.

Troubleshoot DID hardware by checking the following sections:

Software Compatibility

Cisco interface cards are often supported on multiple Cisco IOS releases. Cisco IOS release information is documented in the product data sheet and in Feature Navigator II.

To determine which Cisco IOS releases support your particular router and combination of cards and modules, go to the Software Advisor at

You must have an account on If you do not have an account or have forgotten your username or password, click Cancel at the login dialog box and follow the instructions that appear.


The two-port and four-port DID interface cards support the RJ-11 connector. Illustrations of the connector ports are shown in Figure: Two-Port Analog DID Voice Interface Card and Figure: Four-Port Analog FXS/DID Voice Interface Card. Information about LEDs can be found in the Voice Interface Cards document.

Figure: Two-Port Analog DID Voice Interface Card


Figure: Four-Port Analog FXS/DID Voice Interface Card


For more information about the VIC-2DID interface card, refer to Understanding 2 Port Direct Inward Dial (2 DID) Voice Interface Cards, document ID 15268.

Shutdown Port

Check to make sure that the port is not shut down. 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 from the 'show running-config' command). If these values do not match those of the telephony connection you are making, reconfigure the voice port.

Verifying Direct Inward Dialing Voice-Port Configuration

To verify voice-port configuration, enter the show voice port command. You can specify a voice port or view the status of all configured voice ports. In the following example, the specified port is configured for DID.

 Router# show voice port 1/1/0  
 Foreign Exchange Station with Direct Inward Dialing (FXS-DID) 1/1/0 Slot is 1, Sub-unit is 1,
 Port is 0  
   Type of VoicePort is DID-IN  
   Operation State is DORMANT  
   Administrative State is UP  
   No Interface Down Failure  
   Description is not set  
   Noise Regeneration is enabled  
   Non Linear Processing is enabled  
   Music On Hold Threshold is Set to -38 dBm  
   In Gain is Set to 0 dB  
   Out Attenuation is Set to 0 dB  
   Echo Cancellation is enabled  
   Echo Cancel Coverage is set to 8 ms  
   Playout-delay Mode is set to default  
   Playout-delay Nominal is set to 60 ms  
   Playout-delay Maximum is set to 200 ms  
   Playout-delay Minimum mode is set to default, value 4 ms  
   Playout-delay Fax is set to 300 ms  
   Connection Mode is normal  
   Connection Number is not set  
   Initial Time Out is set to 10 s  
   Interdigit Time Out is set to 10 s  
   Call Disconnect Time Out is set to 3 s  
   Ringing Time Out is set to 180 s  
   Wait Release Time Out is set to 3 s  
   Companding Type is u-law  
   Region Tone is set for US  
   Analog Info Follows:  
   Currently processing none  
   Maintenance Mode Set to None (not in mtc mode)  
   Number of signaling protocol errors are 0  
   Impedance is set to 600r Ohm  
   Station name Chalil Mohanan, Station number 1234567  
   Voice card specific Info Follows:  
   Signal Type is wink-start  
   Dial Type is dtmf  
   In Seizure is inactive  
   Out Seizure is inactive  
   Digit Duration Timing is set to 100 ms  
   InterDigit Duration Timing is set to 100 ms  
   Pulse Rate Timing is set to 10 pulses/second  
   InterDigit Pulse Duration Timing is set to 750 ms  
   Clear Wait Duration Timing is set to 400 ms  
   Wink Wait Duration Timing is set to 200 ms  
   Wait Wink Duration Timing is set to 550 ms  
   Wink Duration Timing is set to 200 ms  
   Delay Start Timing is set to 300 ms  
   Delay Duration Timing is set to 2000 ms  
   Dial Pulse Min. Delay is set to 140 ms  
   Percent Break of Pulse is 60 percent  
   Auto Cut-through is disabled  
   Dialout Delay for immediate start is 300 ms

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