call disconnecting problem in cisco 2851 ccme router

Unanswered Question
Aug 1st, 2010

hi all,

i am facing one issue on analog lines connected to cisco 2851 router

the issue is, when an incoming call comes to reception it is ringing but when she tries to pickup the call is disconnecting automatically.

i dont know from where problem is , also happening in some particular lines.i need to setup any line parameters or.....



I have this problem too.
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Steven Holl Wed, 08/04/2010 - 11:17


Please be more specific when describing a problem.  How is this call coming in?

If calls are coming in an analog FXO port, there's a good chance this is a result of battery reversal.  Try:

voice-port x/x

  no battery-reversal


  no shut

If it is a PRI or SIP trunk, the disconnect may be a codec negotiation issue, in which case, I need more information on the call topology to let you know what you specifically would want to collect to diagnose further.


zeuscyril Thu, 08/05/2010 - 02:39


the calls are coming in through FXO port only



Steven Holl Thu, 08/05/2010 - 06:14

So disabling battery reversal didn't fix it?

If so, get these debugs during the issue:

debug vpm sig

debug voip ccapi inout


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