@ProfTech, you are absolutely right. I just noticed that this morning. While in OBiTalk, I hovered over the question mark next to URI and read, "URI is normally used when the service provider requires a SIP AuthID to be used." Aha!
From the description of the URI parameter on page 115 of the admin manual:
QuoteThis parameter affects the way the AOR [Address of Record] is formed by the device in outbound SIP Requests. The AOR has the format: user@domain.
If the value of URI is empty, device gets the user portion of its AOR from the AuthUserName, and the domain portion the value of ITSP Profile's UserAgentDomain if it is not empty, or that of the ProxyServer otherwise.
If the value URI is not empty and does not contain "@", it is used as the user portion of the AOR while the domain portion is formed the usual way.
...
Note: In all cases, device uses AuthUserName and AuthUserPassword to compute authorization if challenged by a 401 or 407 response.
So the answer is
not AuthUserName or X_ContactUserID. There is no need for OBi Expert config. In OBiTalk, just put the UserID ("110") in the
URI field and the AuthID ("1ComplexID") in the
Username field and voila! the OBi sends the correct packet in response to the 407 Proxy Authentication Required challenge:
From: <sip:
110@192.168.1.100>;tag=SP37fff1fcbfe7f43f5
To: <sip:
110@192.168.1.100>
Via: SIP/2.0/UDP 192.168.1.144:5082;branch=z9hG4bK-bae52b76;rport
Proxy-Authorization: Digest algorithm=MD5,nonce="414d535c11a34a3d28:325d88862ac6bacc590028a4698b6aa0",realm="3CXPhoneSystem",
response="6c7b0f74e9262732e9e0958cad0fa857",uri="sip:192.168.1.100:5060",username="
1ComplexID"
User-Agent: OBIHAI/OBi200-3.2.2.5898
Contact: <sip:
110@192.168.1.144:5082>;expires=60;+sip.instance="<urn:uuid:00000000-0000-0000-0000-9cadef601e4b>"
The issue with not putting an extension-to-extension call through was my fault. I was trying to dial out on the wrong line.