This document explains how to troubleshoot these issues:
This document provides information on potential problems between the
Cisco IP phone and Cisco CallManager.
Ensure that you meet these requirements:
Cisco CallManager Release 4.0(1) Service Release (SR) 1a or
Cisco IP Phone 7940G that runs firmware 6.0.2(1) or
Cisco IP Phone 7960G that runs firmware 6.0.2(1) or
Cisco IP Phone 7970G that runs firmware TERM70.6-0-1-0.sbn01 or
PC with 1GHZ or higher Pentium III, or a compatible
Microsoft Windows 2000 Professional (Service Pack [SP]3 or later) or
Windows XP Professional (SP1 or later)
256 MB RAM minimum
40 MB free disk space
Video capable graphics card at 800x600x16 bit or
One free Universal Serial Bus (USB) 1.1 or 2.0
One free 10/100 Base-T Ethernet interface
256 kpbs minimum bandwidth
Cisco Unified Video Advantage, Release 2.1 supports 32-bit versions
of Windows Vista with 32-bit (x86) processors.
For Cisco Unified Video Advantage that operates with Cisco IP
Communicator or with a Cisco Unified IP Phone, Cisco Unified Communications
Manager Version 4.1(3), Service Release 2 or later is
The information in this document is based on Cisco VT Advantage
installed on Windows 2000 or Window XP.
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.
Technical Tips Conventions for more information on document
This section provides possible causes of remote video loss and explains
how to troubleshoot these issues.
In this picture, the local video works correctly, but the remote is
black with a red X through the connectivity diagram in the application.
VT Advantage requires that your PC receives Ethernet feed directly from
the switched output port on the back of your phone—the one labeled
10/100 PC. Trace the Ethernet cable by hand to ensure that
your PC is properly connected to the back of the IP phone.
Typically, phones are configured on a separate VLAN from computers. If
these two VLANs have a firewall between them, the phone can be prevented from
talking to the PC. The CAST protocol is used to operate between VT Advantage
and the IP phone. The PC must be able to reach the IP phone over TCP/IP. Try to
reach your phone with a browser in order to determine if this is case. Enter
http://xxx.yyy.zzz, where the cryptic part of the URL is the
IP address of your phone. Unless your network administrator has disabled
browsing to the phone, you should browse to the web page of the phone.
The network administrator must allow for the CAST protocol by
configuring the access lists and firewalls to allow for the PC to send CAST
messages to the IP phone over TCP port number 4224. The PC initiates the TCP
connection on TCP port 4224 and the IP phone sends acknowledgement messages
back to the PC on the same port number. Therefore, bidirectional communication
on this port number is required.
Note: The video camera cannot make a connection with the IP phone if the PC
to which the camera is connected uses dual NICs with dual IP address
assignment, or if two IP addresses in different subnets are binded to a single
VT Advantage only works with Cisco 7940, 7960, or 7970 IP Phones that
have both a video-capable firmware load and video enabled by Cisco CallManager.
You can verify this by the presence of a camera icon in the lower right corner
of your IP phone screen. If there is no camera icon, you will not receive
If your phone does not have the video camera icon, ask your network
administrator to make sure you have the proper phone load and that video
enabled is checked on the device configuration page for your IP phone on the
Cisco CallManager Administration page. Complete these steps in order to confirm
the phone load:
VT Advantage is only supported by this and later versions of Cisco
CallManager. Unfortunately, there are no patches available for earlier versions
of Cisco CallManager.
Right-click twice on either of the quality bars in the main window in
order to bring up the VT Advantage diagnostic window.
There is a section in the middle of the window labeled TCP Link
If the Refused field has a number greater than 1 or 2, and particularly
if it continues to increment, your phone rejects the sent packets of VT
Advantage. Sometimes cycling power on the phone corrects this problem,
especially if everything is configured correctly and has worked in the past.
Highlight the Cisco VT Advantage icon on the bottom right tool
tray in order to verify that VT Advantage recognizes the
VT Advantage uses either of these compression formats (codecs) in order
to transmit and receive video. The bit rate of the call depends on the codec
that is used.
The codec and bit rate that is used for the call is controlled through
the use of Regions in Cisco CallManager Administration. VT Advantage does not
present the user with an option to choose the codec or the bit rate of the
call. It is completely controlled by Cisco CallManager. Cisco CallManager
negotiates a common codec and speed between the endpoints on a call-by-call
basis, and instructs the endpoints to open video channels.
The speed at which a VT Advantage client can encode or decode video is
also dependent on the speed of the CPU and the amount of available
You need to configure a Media Control Unit (MCU) in order to video
conference three or more video calls.
Next, the administrator can define what MCU is used to host multiparty
conferences when the user presses the Conf softkey on their IP
phone. This is done by configuring Media Resource Groups (MRGs)/Media Resource
Group Lists (MRGLs) in Cisco CallManager Administration.
The MCU is first added to a MRG. The MRG is then added to a MRGL, and
then the MRGL is assigned to the endpoint. When the user presses the
Conf softkey, Cisco CallManager looks for an available MCU
resource within that IP phone MRGL. Screen shots are not provided because this
is a multi-step configuration process.
Note: Cisco CallManager always uses the first MCU resource found in the
phone MRGL. If an audio-only conference bridge is placed at the top of the
list, Cisco CallManager always uses that conference resource first, even if the
call requires video. Therefore, the administrator must configure the IP/VC MCU
as the first conference resource in the MRG, and make sure that the MRG
contains the MCU listed first in the MRGL.
If you still have problems, you need to further troubleshoot the issue.
Media Resource Groups and Group Lists for more information.