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Weird call forwarding issue when phone off PBX is on call forward.

Hello - have (2) 3600 series routers connected to pbx's doing toll bypass, T1 on one side E1 on the other. All calls work ok and voice quaility is good however when a user on the PBX behind the E1 puts his phone on forward the call fails with a fast busy type of error (actually it rings once then fails) ISDN debugs yield:Cause i = 0x81E020 - Mandatory information element missing then the router disconnects the call.


Re: Weird call forwarding issue when phone off PBX is on call fo

The 'debug isdn q931' command, shows the call progress and the areas of problems. Sometimes the call fails due to a timer expiration. In the debug command output, the time period from when the call proceeding flows until the call fails, gives a guideline for the amount of time required to complete a call connection. The workaround is to wind out timers, which allow the call setup enough time to complete the connection.