I've tried both, and receive different results.
IP: Get authentication failed with and without STUN enabled on headset mode (no extensions listed). However with STUN enabled I do get extensions listed in desk phone mode.
Name: NO authentication failed with and without STUN enabled on headset mode. However no extensions listed in either headset or desk phone mode. Able to receive calls on client fine. Try to make outbound call from client and Forbidden is displayed on client window. Check server log and get the following:
*Edited number dialed to be 5555555, outside IP to be xx.xxx.xxx.xxx, and server name to be sip.domain.com
[CM503008]: Call(212): Call is terminated
14:32:47.999 CallCtrl:

nIncomingCall [CM502001]: Source info: From: 212; To: "3CXPhone [sip:
[email protected]:5060];tag=c928e056[sip:
[email protected]:5060]
14:32:47.999 CallCtrl:

nIncomingCall [CM503013]: Call(212): Incoming call rejected, caller is unknown; msg=SipReq: INVITE
[email protected]:5060 tid=3721c147853d1066 cseq=INVITE
[email protected]:5070 / 2 from(wire)
14:32:47.858 evt::CheckIfAuthIsRequired::not_handled [CM500002]: Unidentified incoming call. Review INVITE and adjust source identification:
INVITE sip:
[email protected]:5060 SIP/2.0
Via: SIP/2.0/UDP 192.168.2.101:5070;branch=z9hG4bK-d8754z-45123070f066ac7f-1---d8754z-;rport=5070;received=xx.xxx.xxx.xxx
Max-Forwards: 70
Contact: [sip:
[email protected]:5070]
To: [sip:
[email protected]:5060]
From: "3CXPhone"[sip:
[email protected]:5060];tag=c928e056
Call-ID: YzdkY2NjM2UzZTE5ODg2NTViZWQ5YmViY2QwMzI3NTQ.
CSeq: 1 INVITE
Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REGISTER, SUBSCRIBE, NOTIFY, REFER, INFO
Supported: replaces
User-Agent: 3CX Phone 6.0.727.0
Content-Length: 0
14:32:47.858 evt::CheckIfAuthIsRequired::not_handled [CM302001]: Authorization system can not identify source of: SipReq: INVITE
[email protected]:5060 tid=45123070f066ac7f cseq=INVITE
[email protected]:5070 / 1 from(wire)
lol so I'm lost. Thanks as usual for your help matt, and understand if you are lost too.