Internal calls can be transferred without problem.
Internal calls to single number reach (SNR) will connect to external number without a problem.
If the external call is answered, the call can be transfered to an external number without any problems.
External calls to SNR or SIP extension with CfwdALL configured will ring on the external number but on connection no audio is heard in either direction, the call signalling (hang up) still works. I have found some posts relating to NAT port and firewall settings but they all seemed to be for Asterix not Cisco.
I have a UC520 running
telephony-service
CONFIG (Version=8.1)
=====================
Version 8.1
Max phoneload sccp version 17
Max dspfarm sccp version 18
Cisco Unified Communications Manager Express
UC520#ext set to forward all
UC520#
309856: Sep 19 14:31:03.685: %SEC-6-IPACCESSLOGP: list 151 denied udp
**.166.**.163(18410) -> **.152.**.234(16580), 1 packet
309857: Sep 19 14:31:05.821: %SEC-6-IPACCESSLOGP: list 151 denied udp
**.238.**.137(23017) -> **.152.**.234(18167), 1 packet
309858: //336901/7205C50DB4F4/SIP/Call/sipSPICallInfo:
The Call Setup Information is:
Call Control Block (CCB) : 0x88104AB8
State of The Call : STATE_ACTIVE
TCP Sockets Used : NO
Calling Number : ****0080452
Called Number : ****3394624
Source IP Address (Sig ): **.152.**.234
Destn SIP Req Addr:Port : **.40.**.175:5060
Destn SIP Resp Addr:Port : **.40.**.175:5060
Destination Name : sip1.voipet.com
309859: //336901/7205C50DB4F4/SIP/Call/sipSPIMediaCallInfo:
Number of Media Streams: 1
Media Stream : 1
Negotiated Codec : g711ulaw
Negotiated Codec Bytes : 160
Nego. Codec payload : 0 (tx), 0 (rx)
Negotiated Dtmf-relay : 6
Dtmf-relay Payload : 101 (tx), 101 (rx)
Source IP Address (Media): **.152.**.234
Source IP Port (Media): 16580
Destn IP Address (Media): **.166.**.163
Destn IP Port (Media): 18410
Orig Destn IP Address:Port (Media): [ - ]:0
309860: //336900/FD4461C91B75/SIP/Call/sipSPICallInfo:
The Call Setup Information is:
Call Control Block (CCB) : 0x8812ACD0
State of The Call : STATE_ACTIVE
TCP Sockets Used : NO
Calling Number : ****0080452
Called Number : ****35822736
Source IP Address (Sig ): **.152.**.234
Destn SIP Req Addr:Port : **.40.**.175:5061
Destn SIP Resp Addr:Port : **.40.**.175:5061
Destination Name : **.40.**.175
309861: //336900/FD4461C91B75/SIP/Call/sipSPIMediaCallInfo:
Number of Media Streams: 1
Media Stream : 1
Negotiated Codec : g711ulaw
Negotiated Codec Bytes : 160
Nego. Codec payload : 0 (tx), 0 (rx)
Negotiated Dtmf-relay : 6
Dtmf-relay Payload : 101 (tx), 101 (rx)
Source IP Address (Media): **.152.**.234
Source IP Port (Media): 18166
Destn IP Address (Media): **.238.**.137
Destn IP Port (Media): 23016
Orig Destn IP Address:Port (Media): [ - ]:0
309862: Sep 19 14:31:07.189: %SEC-6-IPACCESSLOGP: list 151 denied udp
**.166.**.163(18411) -> **.152.**.234(16581), 1 packet
309863: //336901/7205C50DB4F4/SIP/Call/sipSPICallInfo:
The Call Setup Information is:
Call Control Block (CCB) : 0x88104AB8
State of The Call : STATE_DEAD
TCP Sockets Used : NO
Calling Number : ****0080452
Called Number : ****3394624
Source IP Address (Sig ): **.152.**.234
Destn SIP Req Addr:Port : **.40.**.175:5060
Destn SIP Resp Addr:Port : **.40.**.175:5060
Destination Name : sip1.voipet.com
309864: //336901/7205C50DB4F4/SIP/Call/sipSPIMediaCallInfo:
Number of Media Streams: 1
Media Stream : 1
Negotiated Codec : g711ulaw
Negotiated Codec Bytes : 160
Nego. Codec payload : 0 (tx), 0 (rx)
Negotiated Dtmf-relay : 6
Dtmf-relay Payload : 101 (tx), 101 (rx)
Source IP Address (Media): **.152.**.234
Source IP Port (Media): 16580
Destn IP Address (Media): **.166.**.163
Destn IP Port (Media): 18410
Orig Destn IP Address:Port (Media): [ - ]:0
309865: //336901/7205C50DB4F4/SIP/Call/sipSPICallInfo:
Disconnect Cause (CC) : 16
Disconnect Cause (SIP) : 200
309866: //336900/FD4461C91B75/SIP/Call/sipSPICallInfo:
The Call Setup Information is:
Call Control Block (CCB) : 0x8812ACD0
State of The Call : STATE_DEAD
TCP Sockets Used : NO
Calling Number : ****0080452
Called Number : ****35822736
Source IP Address (Sig ): **.152.**.234
Destn SIP Req Addr:Port : **.40.**.175:5061
Destn SIP Resp Addr:Port : **.40.**.175:5061
Destination Name : **.40.**.175
309867: //336900/FD4461C91B75/SIP/Call/sipSPIMediaCallInfo:
Number of Media Streams: 1
Media Stream : 1
Negotiated Codec : g711ulaw
Negotiated Codec Bytes : 160
Nego. Codec payload : 0 (tx), 0 (rx)
Negotiated Dtmf-relay : 6
Dtmf-relay Payload : 101 (tx), 101 (rx)
Source IP Address (Media): **.152.**.234
Source IP Port (Media): 18166
Destn IP Address (Media): **.238.**.137
Destn IP Port (Media): 23016
Orig Destn IP Address:Port (Media): [ - ]:0
309868: //336900/FD4461C91B75/SIP/Call/sipSPICallInfo:
Disconnect Cause (CC) : 16
Disconnect Cause (SIP) : 200
UC520#
UC520#call connects, no audio in either direction
