If your initial efforts to troubleshoot are not successful, you could
be required to use traces. This allows you to analyze what component has failed
with Cisco VT Advantage. This document discusses the use of trace tools
provided with Cisco VT Advantage and how to understand them.
Readers of this document should have knowledge of these topics:
The information in this document is based on these software and
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.
For more information on document conventions, refer to the
Technical Tips Conventions.
These sections provide information to help you view and interpret CAST
From the Start menu, open the Cisco VT Advantage
Diagnostics window. As shown in Figure 1, there are three buttons,
labeled Update Status, CDP Viewer, and CAST Viewer, at roughly 6:00 in this
Figure 1 – Diagnostics Window
If you press the CAST Viewer button, a dialog box
appears. You can use this box in order to view what Cisco CallManager sends.
Figure 2 is an example of the CAST Viewer dialog box you see.
Figure 2 – CAST Viewer Dialog
There is a great deal of information in this dialog box. However, in
order to track your video call, you really only need to examine the trace
messages. Here is some information to help you troubleshoot your video problem
with the CAST Viewer dialog box:
On the right-hand side of the dialog box, you see a list of messages
that are exchanged between Cisco VT Advantage and the Cisco CallManager. If you
use your mouse in order to select one of the messages, the detail in the
Message Breakdown window expands on the right-hand side as well (see
Note: There are a series of messages, all around 12:52. There is a long
series of call status messages that are sent while the call is set up. These
let Cisco VT Advantage know what state the phone is in at any given
Note: Although these messages provide additional information, all you
really need to examine is the message highlighted in Figure 2. The
OpenMultiMediaReceiveChannel message is sent by
the Cisco CallManager in order to indicate that a video stream is going to be
sent to the PC.
If you see the
OpenMultiMediaReceiveChannel message, a
corresponding acknowledgment sent by Cisco VT Advantage is visible. If you do
not see this message, no video was sent and none is expected.
The Cisco CallManager also sends a command that tells Cisco VT
Advantage to send video. This comes in the form of a
StartMultimediaTransmission message, which tells
Cisco VT Advantage to begin video transmission. Without this message, no video
You can bring up the CAST Viewer dialog box at any time, and this
dialog box shows you a trace of the messages that were sent during your call.
You can also save the contents of the message buffer to a file for later
analysis or in order to help Cisco Technical Support troubleshoot your video
If video was not enabled with your call, look at the CAST Viewer first.
This example has a sequence of station information messages, but no commands to
send or receive multimedia data. What does a message buffer, such as the one in
Figure 3, mean?
Figure 3– CAST Messages
If you see a sequence of station information messages but no commands
to send or receive multimedia data, for some reason the Cisco CallManager
decided this was not a video call. There are a number of possible reasons for
The remote end did not report that the call is video
The remote end is video enabled, but you do not have a compatible set
of coder-decoders (codecs).
The remote end is video enabled, but needed conference resources are
All of these are possibilities. More often than not, if you see the
CAST messages and do not see any messages that ask to initiate video
transmission, there is nothing wrong. Most likely, the Cisco CallManager
decided for legitimate reasons not to use video on the call.