Configuring Voice Ports

We have now discussed the basic hardware installation for VNMs and VICs. The next step is to configure the cards on the Cisco router IOS. Voice card configuration is covered in the following sections. Some basic configuration parameters must be set in order for a voice port to operate. To configure a voice port, complete the following steps.

1. 
   
   Enter Privileged Exec mode:

   router> enable
   

2. 
   
   Check the DSP voice channel activity with the following command:

   router# show voice dsp
   

3. 
   
   Enter Global Configuration mode:

   router# configure terminal
   

4. 
   
   Enter Voice Card Configuration mode. On the router, the slot must be 0:

   router(config)# voice-card slot
   

5. 
   
   Enter the CODEC type for the voice card:

   router(config-voicecard)# CODEC {med | high} 

This series of steps sets the CODEC compression technique, which is either high or medium complexity. High complexity can handle fewer calls per DSP. This is due to the higher CPU utilization required for high CODEC complexity operation. High and medium complexity CODECs:

• 
  
  High complexity Specifies two voice channels encoded in any of the following formats: G.711ulaw, G.711alaw, G.723.1 (r5.3), G.723.1 Annex A (r5.3), G.723.1 (r6.3), G.723.1 Annex A (r6.3), G.726 (r16), G.726 (r24), G.726 (r32), G.728, G.729, G.729 Annex B, and fax relay.
• 
  
  Medium (default) complexity Specifies four voice channels encoded in any of the following formats: G.711ulaw, G.711alaw, G.726 (r16), G.726 (r24), G.726 (r32), G.729 Annex A, G.729 Annex B with Annex A, and fax relay.

Configuring FXO or FXS Voice Ports

All these parameters have default settings, and FXS and FXO port default configuration values are adequate for most situations. Therefore, user intervention is rarely needed. The following settings are mandatory to any FXS/FXO port configuration:

• 
  
  Signal type
• 
  
  Call progress tone
• 
  
  Ring frequency
• 
  
  Ring number
• 
  
  Dial type (FXO only)
• 
  
  PLAR connection mode
• 
  
  Music threshold
• 
  
  Description
• 
  
  Voice activity detection (VAD)
• 
  
  Comfort noise

Follow these steps to complete a basic setup for all FXS/FXO voice ports:

1. 
   
   Enter Privileged Exec mode:

   router> enable
   

2. 
   
   Enter Global configuration mode:

   router# configure terminal
   

3. 
   
   Identify which port to configure on a 2600 and 3600 series router:

   router(config)# voice-port nm-module/vic-module/port-number
   router(config)# voice-port slot/port   (Cisco 175x/1760 and MC3810)

4. 
   
   Select the appropriate signaling for the start of a call:

   router(config-voiceport)# signal [loop-start|ground-start]
   

5. 
   
   Select the appropriate country codes for call progression signaling. The default is northamerica:

   router(config-voiceport)# cptone country-code
   

6. 
   
   Configure the voice port connection mode type. If the connection will be to a PBX, use the tie-line option. If the connection will be for private line automatic ringdown (PLAR), use the plar option. If the connection will be for PLAR off-premises extension (OPX), use the plar-opx option.

   router(config-voiceport)# connection {tie-line | plar | plar-opx} string
   

7. 
   
   Assign the appropriate out-dialing dial type (FXO only):

   router(config-voiceport# dial-type{dtmf | pulse}
   

8. 
   
   Configure the frequency in Hertz of ringing for the system that is attached on a Cisco 1750, 2600, and 3600 series router (FXS only):

   router(config-voiceport)# ring frequency [25| 50]
   router(config-voiceport)# ring frequency [20| 30] 

9. 
   
   Configure the maximum number of rings allowed before answering a call (FXO only):

   router(config-voiceport)# ring number number
   

10. 
    
    Specify an existing pattern for ring tone or define a new one (FXS only). Each pattern specifies a ring-pulse time and a ring-interval time:

    router(config-voiceport)# ring cadence {[pattern01 | pattern02 … pattern12]
    [define pulse interval]}
    

11. 
    
    Specify the termination impedance, which needs to match the specifications of the PBX it is attaching to:

    router(config-voiceport)# impedance [600c|600r|900c|complex1|complex2]
    

12. 
    
    Configure the threshold in decibels for hold music:

    router(config-voiceport)# music-threshold number
    

13. 
    
    (Optional) Configure a text string to the configuration that describes the connection for this voice port:

    router(config-voiceport)# description string
    

14. 
    
    Configure background noise generation for the comfort of a user when there is no noise:

    router(config-voiceport)# comfort-noise
    

15. 
    
    (Optional) Enable voice activity detection:

    router(config-voiceport)# vad
    

Configuring E&M Ports

E&M default settings are usually not sufficient to enable voice transmissions over IP. This is because E&M ports are designed to connect directly to a PBX and therefore must match the particular PBX's specifications. The following settings are mandatory to implement an E&M port:

• 
  
  Signal type
• 
  
  Call progress tone
• 
  
  Operation
• 
  
  Type
• 
  
  Impedance

The following commands complete a basic setup for all E&M voice ports:

1. 
   
   Enter Privileged Exec mode:

   router> enable
   

2. 
   
   Enter Global Configuration mode:

   router# configure terminal
   

3. 
   
   Identify which port to configure on a 2600 and 3600 series router:

   router(config)# voice-port nm-module/vic-module/port-number
   router(config)# voice-port slot/port (Cisco 175x/1760 and MC3810)

4. 
   
   Select the appropriate signaling for the interface:

   router(config-voiceport)# signal [wink-start|immediate|delay-dial]

5. 
   
   Select the appropriate country codes for call progression signaling. The default is us. The northamerica keyword is for the Cisco MC3810 multiservice concentrator for versions prior to Cisco IOS Release 12.0(4)T and for ISDN PRI:

   router(config-voiceport)# cptone country code
   

6. 
   
   Define cabling scheme operation:

   router(config-voiceport)# operation [2-wire|4-wire]
   

7. 
   
   Select the appropriate E&M interface type:

   router(config-voiceport)# type [1|2|3|5]
   

8. 
   
   Specify the termination impedance, which needs to match the specifications of the PBX the port is attaching to:

   router(config-voiceport)# impedance [600c|600r|900c|complex1|complex2]
   

Some optional configurations for the E&M port are not required for operation. As with the FXS/FXO ports, the following configurations are used for optimization and usability:

• 
  
  Connection mode
• 
  
  Music threshold
• 
  
  Description
• 
  
  Comfort tone (VAD-activated only)

Use the following commands to adjust any of these optional configuration parameters for E&M ports:

1. 
   
   Enter Privileged Exec mode:

   router> enable
   

2. 
   
   Enter Global Configuration mode:

   router# configure terminal

3. 
   
   Identify which port to configure on a 2600 and 3600 series router:

   router(config)# voice-port nm-module/vic-module/port-number
   router(config)# voice-port slot/port (Cisco 175x/1760 and MC3810)
   

4. 
   
   Specify that the port configured for PLAR 

   router(config-voiceport)# connection plar string
   

5. 
   
   Define the threshold in decibels for hold music:

   router(config-voiceport)# music-threshold number
   

6. 
   
   Specify a description field for port:

   router(config-voiceport)# description string
   

7. 
   
   Set comfort noise to generate background noise for the user when there is no sound on the line:

   router(config-voiceport)# comfort-noise