Cisco Unified IP Phone 8941 Administration Manual page 180

General Troubleshooting Information
Summary
Moving a network connection
from the phone to a workstation.
Changing the telephone
configuration.
Phone resetting.
Codec mismatch between the
phone and another device.
Sound sample mismatch
between the phone and another
device.
Loopback condition.
Related Topics
Apply a Phone Password, on page 31
Display Call Statistics Window, on page 148
Cisco Unified IP Phone 8941 and 8945 Administration Guide for Cisco Unified Communications Manager 10.0
(SCCP and SIP)
166
Explanation
If you are powering your phone through the network connection, you must
be careful if you decide to unplug the phone network connection and plug
the cable into a desktop computer.
The network card of the computer cannot receive power through
Caution
the network connection; if power comes through the connection,
the network card can be destroyed. To protect a network card,
wait 10 seconds or longer after unplugging the cable from the
phone before plugging it into a computer. This delay gives the
switch enough time to recognize that there is no longer a phone
on the line and to stop providing power to the cable.
By default, the network setup options are locked to prevent users from
making changes that could impact their network connectivity. You must
unlock the network setup options before you can configure them.
The phone resets when it loses contact with the Cisco Unified
Communications Manager software. This lost connection can be due to
any network connectivity disruption, including cable breaks, switch outages,
and switch reboots.
The RxType and the TxType statistics show the codec that is being used
for a conversation between this Cisco Unified IP phone and the other
device. The values of these statistics should match. If they do not, verify
that the other device can handle the codec conversation, or that a transcoder
is in place to handle the service.
The RxSize and the TxSize statistics show the size of the voice packets
that are being used in a conversation between this Cisco Unified IP phone
and the other device. The values of these statistics should match.
A loopback condition can occur when the following conditions are met:
• The SW Port Configuration option in the Network Setup menu on
the phone is set to 10 Half (10-BaseT / half duplex)
• The phone receives power from an external power supply
• The phone is powered down (the power supply is disconnected)
In this case, the switch port on the phone can become disabled and the
following message will appear in the switch console log:
HALF_DUX_COLLISION_EXCEED_THRESHOLD
To resolve this problem, enable the port from the switch.