This document describes how to troubleshoot a scenario where Cisco Voice Portal (CVP) Call Server receives the error message “401 Unauthorized” in the CVP Comprehensive Call Flow when the call is transferred to an agent.
Cisco recommends that you have knowledge of these topics:
The information in this document is based on CVP Server 8.5 and above
The information in this document was created from the devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If your network is live, make sure that you understand the potential impact of any command.
This issue was reproduced in a regular CVP comprehensive call flow setup with CVP, Voice XML (VXML) Gateway, CUBE, and Cisco Unified Communication Manager (CUCM).
G729r8 codec is used between provider and CUBE. From CUBE to CVP, the codec used is G711ulaw. CUBE invokes a transcoder resource in order to transcode G729r8 to G711ulaw for self-service prompt, and conversation with agent phones.
When the call is placed, the self-service leg of the call, with G711u codec works fine (when the call is between CVP and VXML for IVR treatment). The issue happens when an agent becomes available, and the call is transferred to the agent; once the agent pick-up the phone, the call is dropped.
The symptoms are very similar to the issues related to media negotiation, MTP, and transcoder resources.
Step1. Enable SIP stack traces in CVP and collect CUBE configuration and version (On CUBE, run the command show run and show version).
Step 2. Reproduce the problem and collect the CVP Call Server logs.
Step 3. Analyze CVP call Server logs.
CVP intiates an INVITE to CUCM in order to establish the call with agent extention 4029.
Step 2. On the Voice Service Voip section in CUBE, the command midcall-signaling passthru is configured. Therefore, the RE-INVITE that CUBE receives is passed to the provider. The provider then, replies with "401 Unauthorized" message to challenge the call, since the provider had not expected a mid-call event.
Step 3. The command midcall-signaling passthru media-change, added to the Voice Service VOIP section in CUBE stops the "401 Unauthorized" error message. CUBE handles this mid-call INVITE locally, which complete the SIP signaling and the agent can answer the call.