Cisco 7975G Software Manual page 252

General Troubleshooting Information
Summary
Prolonged broadcast storms
cause IP phones to reset, or be
unable to make or answer a call
Moving a network connection
from the phone to a workstation
Changing the telephone
configuration
Codec mismatch between the
phone and another device
Sound sample mismatch
between the phone and another
device
Gaps in voice calls
Cisco Unified IP Phone 7975G, 7971G-GE, 7970G, 7965G, and 7945G Administration Guide for Cisco Unified
Communications Manager 9.0 (SCCP and SIP)
232
Explanation
A prolonged Layer 2 broadcast storm (lasting several minutes) on the voice
VLAN may cause IP phones to reset, lose an active call, or be unable to
initiate or answer a call. Phones may not come up until a broadcast storm
ends.
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 computer network card cannot receive power through the
Caution
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 no phone is on the line
and to stop providing power to the cable.
By default, the network configuration options are locked to prevent users
from making changes that could impact their network connectivity. You
must unlock the network configuration options before you can configure
them. See Unlock and Lock Options, on page 63
The RxType and the TxType statistics show the codec that is 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.
See Call Statistics Screen, on page 191
these statistics.
The RxSize and the TxSize statistics show the size of the voice packets
that are used in a conversation between this Cisco Unified IP phone and
the other device. The values of these statistics should match.
See Call Statistics Screen, on page 191
these statistics.
Check the AvgJtr and the MaxJtr statistics. A large variance between these
statistics might indicate a problem with jitter on the network or periodic
high rates of network activity.
See Call Statistics Screen, on page 191
these statistics.
Troubleshooting and Maintenance
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