Lab Exercise: Voice Port Configuration
In this lab, you will configure and test router R1's FXS port using the topology you constructed in the lab exercise for Chapter 2, "Analog and Digital Voice Connections." Recall that an FXS port allows you to connect end stations, such as analog phones, fax machines, and modems, into a voice-enabled router.
Figure 3-19 illustrates the lab's physical topology and IP addressing.
Figure 3-19 Lab Topology
Task 1: Configure FXS Port Parameters
In this task, you will issue commands to configure various parameters on an FXS port.
Complete these steps:
- Enter voice port configuration mode for the FXS port on router R1.
- To ensure the appropriate signaling type on this voice port, configure the signaling to the default value of loopstart.
- Assume the analog phone connected to this voice port is located in one of several adjoining cubicles and you wish to create a distinctive ring for this phone so that the phone's user can distinguish their phone's ringing pattern from other phones' ringing patterns. Create a distinctive ringing pattern that causes the analog phone to ring for 5 seconds, be silent for 1 second, and then repeat this pattern. To make sure this change takes effect, shut down and then bring up the voice port, using the shutdown command, followed by the no shutdown command.
- Assume that several thousand feet of cable separate the analog phone from the FXS port, and as a result, some electrical capacitance has built up in the line. This capacitance can lead to an impedance mismatch, thus causing echo. To help counteract this capacitance, change the impedance value of the voice port from the default value of 600r (that is, 600 purely resistive ohms) to 600c (that is, 600 ohms of impedance that contains both a resistive and a capacitive component).
Task 2: Exercise Verification
In this task, you will verify the parameters you configured are in effect and that the FXS port is functioning properly.
Complete these steps:
- To verify that the appropriate signaling, ring cadence, and impedance settings are applied to R1's FXS port, use the show voice port port_id command to view the port settings.
- To verify that the voice port is functioning, lift the handset of the attached analog phone. You should hear dial tone. If you do not hear dial tone, you might need to administratively bring up the port with the no shutdown command.
- To verify that the voice port can send a ringing signal at an appropriate voltage and frequency as to alert the attached analog phone, enter the test voice port port_id relay ring on command, followed by the test voice port port_id relay ring disable command.
Although your physical hardware might differ, Example 3-9 offers one solution to the preceding exercise.
Example 3-9. Router R1's Configuration
R1#configure terminal Enter configuration commands, one per line. End with CNTL/Z. R1(config)#voice-port 1/1 R1(config-voiceport)#signal loopstart R1(config-voiceport)#ring cadence define 50 10 R1(config-voiceport)#shutdown R1(config-voiceport)#no shutdown R1(config-voiceport)#impedance 600c R1(config-voiceport)#end
The results of the show voice port port_id command, issued on router R1, should be similar to the output shown in Example 3-10. Note that the shaded lines in the output reflect the parameters configured in this exercise
Example 3-10. Router R1's show voice port 1/1 Output
R1#show voice port 1/1 FXS 1/1 Slot is 1, Port is 1 Type of VoicePort is FXS 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 Non Linear Mute is disabled Non Linear Threshold is -21 dB 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 Cancellation NLP mute is disabled Echo Cancellation NLP threshold is -21 dB Echo Cancel Coverage is set to 64 ms Echo Cancel worst case ERL is set to 6 dB Playout-delay Mode is set to adaptive 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 40 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 60 s Supervisory Disconnect Time Out is set to 750 ms Ringing Time Out is set to 180 s Wait Release Time Out is set to 30 s Companding Type is u-law Coder Type is g729ar8 Voice Activity Detection is enabled Nominal Playout Delay is 60 milliseconds Maximum Playout Delay is 200 milliseconds 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 600c Ohm Analog interface A-D gain offset = -3.0 dB Analog interface D-A gain offset = -3.0 dB FXS idle voltage set to low Station name None, Station number None Translation profile (Incoming): Translation profile (Outgoing): Voice card specific Info Follows: Signal Type is loopStart Ring Frequency is 20 Hz Hook Status is On Hook Ring Active Status is inactive Ring Ground Status is inactive Tip Ground Status is active Digit Duration Timing is set to 100 ms InterDigit Duration Timing is set to 100 ms Hookflash-in Timing is set to 1000 ms Hookflash-out Timing is set to 400 ms No disconnect acknowledge Ring Cadence is User defined Ring Cadence are [50 10] * 100 msec Ringer Equivalence Number is set to 1 InterDigit Pulse Duration Timing is set to 500 ms