Thank you Charles for your reply.
So, if I well understood, there is no desktop ip phone able to connect directly at the 3CX using tunnel, right ?
This mean that, if I want to use this method (to reduce nat/sip/rtp issues and limit licenses usage with in-lan extensions communications) the only way is to install on a local server the Session Border Controller, right ?
If yes, could you clarify me if it is necessary configure something on firewall or stun to permit communications from SBC to 3CX (installed in cloud on a public ip address) ?
I installed SBC on a Win2k8R2 but don't work.
Analyzing log files, I found tons of this two row:
ALERT | 20151209-074409.000 | 3CXTunnel | TUNL | 1640 | TunnelTcp.cpp:344 | Sending first packet from [ V4 0.0.0.0:6013 UNKNOWN_TRANSPORT target domain=unspecified mFlowKey=0 ] to [ V4 My3CxIpAddress:5090 TCP target domain=unspecified mFlowKey=0 ]
ERR | 20151209-074409.046 | 3CXTunnel | TUNL | 1640 | TunnelTcp.cpp:159 | Bridge [3CXSBC14.0.45961.29] failure 'Connection is terminated by peer - while begin to read a packet from tunnel' on TCP connection: TunnelTcp:

rocess
This is the config file:
[Log]
Type=file # cout, cerr, file, syslog
File=C:\ProgramData\3CXSBC\Logs\3cxsbc.log
Level=ERR # NONE", "EMERG", "ALERT", "CRIT", "ERR", "WARNING", "NOTICE", "INFO", "DEBUG", "STACK", "ERR", "VERBOSE"
[Bridge/123456]
Name=3CXSBC14.0.45961.29
ID=123456
#LocalSipPort=5060 # local SIP (UDP/TCP) address (def: 5060)
#LocalSipAddr=0.0.0.0
PbxSipIP=My3CxIpAddress
PbxSipPort=5060
Password="myPassword"
SecurityMode=0
TunnelAddr=My3CxIpAddress
TunnelPort=5090
[General]
PrintStatsInterval=30
ReconnectInterval=30
Could you help me to understand where is the issue ?
Thank you for support