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FXO ports

Unanswered Question
Sep 23rd, 2008
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Hi there,

I have a gateway that is connectec to a PBX using VIC2-4FXO

Frequently those ports keep "bloqued" after being used... and it is necessary to shutdown the ports to make them work again...

This is a example of a port config. Any suggestion for solve this problem ?

voice-port 0/0/3

playout-delay nominal 250

playout-delay minimum high

playout-delay mode fixed

cptone BR

timeouts interdigit 3



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Overall Rating: 4 (1 ratings)
jamesfang98 Mon, 09/29/2008 - 07:06
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Here is the summary for FXO disconnect problem:

Problems with FXO

At the end of a VoIP call, both ends hang up the phone or terminate the call. You would expect that all gateway ports involved with the end-to-end call would also disconnect. Sometimes this is not the case with FXO ports when using loop start signaling. There is a common problem known as the FXO disconnect problem.

The FXO port looks like a phone to the central office switch or PBX. The FXO interface closes the loop and the C.O. provides constant battery on the wire. Therefore, there is no disconnect supervision. Just as the switch expects a user to hang up the phone when the call is complete, it also expects the FXO port to hang up. There is no automated process in the router that tells the FXO to disconnect when a call is completed. This is why FXO ports can sometimes become hung up or continue to send ring tones after the call has already cleared. The FXO expects the C.O. switch or PBX to tell it when to hang up. If the local FXO initiated the call and sent it out of its FXO port, then it can supply local disconnect. If it's receiving a call on its FXO then it needs to have a disconnect signal from the PSTN or PBX. Now, there's always a work-around for everything. Here is a list of some of the methods Cisco uses to get around this problem.

Ground-start Signaling Disconnect

Power Denial-based Supervisory Disconnect

Battery Reversal

Tone-based Supervisory Disconnect

Here is solution:

voice-port 0/0/3

timeouts call-disconnect 120 (seconds)

If help pls rate

andrei.goncalves Mon, 09/29/2008 - 10:11
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Am I reading this right ?

Is the call comming from one port and going out for another port ?

R_Manaus#sh call activ voice brief

Total call-legs: 2

1821 : 1526 630373900ms.1 +6540 pid:3203 Answer active

dur 00:08:58 tx:0/0 rx:0/0

Tele 0/0/3 (1526) [0/0/3] tx:0/0/0ms None noise:0 acom:0 i/0:0/0 dBm

1821 : 1528 630378320ms.1 +2120 pid:3200 Originate 3276 active

dur 00:08:58 tx:0/0 rx:0/0

Tele 0/0/0 (1528) [0/0/0] tx:0/0/0ms None noise:0 acom:0 i/0:0/0 dBm



jamesfang98 Mon, 09/29/2008 - 11:58
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I went throught the doc and it did present the tunning options for FXO disconnect supervisor.

Did you ever try one?

For your 'show call active voice brief', it looks two call legs (one incoming to 0/0/3, one outoing from 0/0/0).

As you pointed out you have 4 FXO ports. You may have dial peer to utilitze the call flows to use both FXO ports (0/0/0 & 0/0/3) for some call at same time as in/out.

For disconnect superviosr, can you post output of:

show voice port 0/0/0

robertdm1973 Thu, 10/16/2008 - 09:55
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James, I'm reading the threads and I have a similar disconnect problem on my FXO ports to Avaya IP406 PBX.

I set-up my voice port as below, it almost fix the problem. But there are stil instances that the port remain 'off-hook' even when no calls are active. Any suggestions?

voice-port 0/0/1

supervisory disconnect dualtone mid-call

no battery-reversal

cptone GB

timeouts call-disconnect 5

timeouts wait-release 5

impedance complex2

andrei.goncalves Thu, 10/16/2008 - 10:31
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Hi, sorry for taking so long...

Here is the voice port output:


Foreign Exchange Office 0/0/0 Slot is 0, Sub-unit is 0, Port is 0

Type of VoicePort is FXO

Operation State is UP

Administrative State is UP

The Last Interface Down Failure Cause is Administrative Shutdown

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 3 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 fixed

Playout-delay Nominal is set to 250 ms

Playout-delay Maximum is set to 250 ms

Playout-delay Minimum mode is set to high, 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 3 s

Call Disconnect Time Out is set to 60 s

Ringing Time Out is set to 180 s

Wait Release Time Out is set to 30 s

Companding Type is u-law

Region Tone is set for BR

Analog Info Follows:

Currently processing Voice

Maintenance Mode Set to None (not in mtc mode)

Number of signaling protocol errors are 0

Impedance is set to 600r Ohm

Station name None, Station number None

Translation profile (Incoming):

Translation profile (Outgoing):

Voice card specific Info Follows:

Signal Type is loopStart

Battery-Reversal is enabled

Number Of Rings is set to 1

Supervisory Disconnect is signal

Answer Supervision is inactive

Hook Status is Off Hook

Ring Detect Status is inactive

Ring Ground Status is inactive

Tip Ground Status is inactive

Dial Out Type is dtmf

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

Percent Break of Pulse is 65 percent

GuardOut timer is 2000 ms

Minimum ring duration timer is 125 ms

Hookflash-in Timing is set to 600 ms

Hookflash-out Timing is set to 400 ms

Supervisory Disconnnct Timing is set to 350 ms




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