How to fix Cisco FXO Voice Card Disconnect issue

How to fix Cisco FXO Voice Card Disconnect issue

Recently, I was working on setting up PSTN/POTS line at international office. On Cisco 2921 router, we installed two of Cisco FXO card. One of the major issues was configuring Cisco FXO card to disconnect the call from outside(inbound call).
It is known issue with carrier tone that is different all over the world.
Basically, Cisco router/FXO card doesn’t recognize disconnect tone from Telecom company.

To fix this problem, there are few step to go

1. Using Cisco cptone option that is predefined.

voice class custom-cptone MYTONE
dualtone disconnect
frequency 425
cadence 350 350

voice-port 0/1/0
trunk-group PSTN
supervisory disconnect dualtone mid-call
supervisory custom-cptone MYTONE
timeouts call-disconnect 2
timeouts wait-release 2
timing hookflash-out 250
connection plar 8005
impedance complex 1
caller-id enable

2. Using custom cptone

voice class custom-cptone Disconnect SIEMENS
dualtone disconnect
frequency 425
cadence 425 325 250 500

voice class custom-cptone Disconnect ERICSSON
dualtone disconnect
frequency 425
cadence 325 325

voice class custom-cptone Disconnect FETEX
dualtone disconnect
frequency 425
cadence 375 375

voice class custom-cptone Disconnect ALCATEL
dualtone disconnect
frequency 425
cadence 375 375

You would have to order ground start trunks from the telco. At least in the US most lines are loop start by default, we had to order ground starts. Its nice though because you get signaling over the trunk so you don’t encounter “glare.”

3. Monitoring and Maintaining FXO Answer and Disconnect Supervision

Router# show voice port 1/0/0

3-1. Unbreakable Dial Tone
; A common problem encountered in a VoIP network is being unable to break dial tone. The router puts a seizure on the local PBX but when digits are dialed, the dial tone stays. The calling party is unable to pass the DTMF tones or digits to the terminating device, resulting in callers being unable to dial the desired extension or interact with the device that needs DTMF tones, such as a voice mail or IVR application. Here are some possible causes of the problem:

– DTMF tones not being sent.
– DTMF tones not being understood.
– DTMF tones too distorted to be understood.
– Other signaling and cabling issues.

Make sure the dial type is set as DTMF on both the router and the PBX. The FXS port does not pass on the digits, therefore this setting is not available on an FXS port. However, this setting can be changed on FXO and E&M ports:

Router(config-voiceport)# dial-type dtmf / mf / pulse

4. Useful commands

Router# test voice tons XX show
Router# debug voice ccapi inout
Router# debug voice vtsp all
Router# debug vpm signal
Router# debug h335 asn1
Router# debug h225 asn1

Ref.

Tone database : http://www.thisisarecording.com/index.html (under international signaling section)
http://www.3amsystems.com/World_Tone_Database
http://www.cisco.com/c/en/us/support/docs/voice/analog-signaling-e-m-did-fxs-fxo/8120-fxo-disconnect.html

http://www.learnios.com/viewtopic.php?f=4&t=30374&start=20

http://docwiki.cisco.com/wiki/Cisco_IOS_Voice_Troubleshooting_and_Monitoring_–_FXO_Interfaces