I have a UC540 with a SIP trunk. The incoming calls are answered by CUE, the caller hears a greeting message and then is connected to the operator.
If the operator activate the CFA, the calls are forwarded to her mobile but the call is disconnected after 30 seconds.
If I program the incoming calls to go directly to operator phone (without greeting message on CUE) then there is no problem with CFA.
The Provider of SIP trunk make his tests and it says that the UC540 disconnects the call. I think they have right because the UC540 sends first the BYE message. See below debug ccsip messages:
000705: Sep 15 14:33:29.860: //-1/xxxxxxxxxxxx/SIP/Msg/ccsipDisplayMsg:
BYE sip:[email protected]:5060 SIP/2.0
Via: SIP/2.0/UDP 172.21.16.145:5060;branch=z9hG4bK5EE12C4
From: 35722100444 <sip:[email protected];user=phone>;tag=E27CCBC0-20C2
To: 25811102 <sip:[email protected];user=phone>;tag=103465381
Date: Wed, 15 Sep 2010 14:32:57 GMT
Call-ID: [email protected]
CSeq: 102 BYE