Dial-peer showing Operational UP when no line connected to FXO

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Apr 7th, 2009
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Hi,


I've noticed when there is no PSTN line terminated on FXO, still the dial-peer Operational status is shown as "UP". I've VIC2-4FXO where PSTN is terminated on two ports only. The dial-peers are configured for all 4 ports.


It is causing outbound calls hiting such dial-peer randomly and then falling-back to others. By the time call-reaches the working dial-peer, it seems the "timeout wait-release 3" is causing call failure.


I've shut down all such dial-peers and now everything works fine for me. I could've increased the timeout wait-release but curious to know if its a normal behavior of FXO ports.


I am trying to compare it with Dial-peers pointed to digital voice-ports (ISDN PRI), where when interface goes down, the dial-peers becomes OPERATIONAL DOWN.


I've Cisco 2811 running c2800nm-advipservicesk9-mz.124-11.T.bin.


Thanks,

inner_silence



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Nicholas Matthews Tue, 04/07/2009 - 14:57
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Hi,


You need to think about the FXO port as if it was an analog phone.


When your phone is on hook, there isn't a reliable way of knowing whether the phone line is connected or not. This requires going off hook, checking for an off-hook voltage, and listening to dial tone.


The best practice for this scenario is to only configure dial peers that you know that are in use.



hth,

nick

Kapil Atrish Wed, 04/08/2009 - 07:52
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Thanks for you reply Nick,


So you mean it is normal to see dial-peers pointing to Analog ports as always Operational UP?


Could you point me to some Doc highlighting this behavior? I did some research but couldn't locate one.


thanks,

inner_silence

Kapil Atrish Wed, 04/08/2009 - 20:24
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Hi Polo,


thanks for your inputs.


I went through this doc, it talks about only the digital voice-ports. I wanted to know how dial-peers operational status behaves when pointed to Analog voice-ports.


I think based on your's and Nick's comments, I can believe there is nothing wrong and DP pointing to analog voice-port always remains up. If I've access to I'll check it in some other scenarios as well may be with FXS/E&M ports this time.


Thanks to both of you for your time.


thanks,

innter_silence

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