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Cisco Unified IP Phone Administration Guide for Cisco Unified Communications Manager 8.0
OL-21035-01
Chapter 6 Troubleshooting and Maintenance
General Troubleshooting Tips
Prolonged broadcast storms
cause phones to reset, or be
unable to make or answer a call
A prolonged Layer 2 broadcast storm (lasting several minutes) on
the voice VLAN may cause 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.
Moving a network connection
from the phone to a workstation
If you are powering your phone through the network connection,
you must be careful if you decide to unplug the phone’s network
connection and plug the cable into a desktop computer.
Caution The computer’s network card cannot receive power
through 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.
Changing the phone
configuration
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.
Dual-Tone Multi-Frequency
(DTMF) delay
When you are on a call that requires keypad input, if you press the
keys too quickly, some of them might not be recognized.
Codec mismatch between the
phone and another device
The RxType and the TxType statistics show the codec that is being
used for a conversation between this ATA 187 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.
Sound sample mismatch
between the phone and another
device
The RxSize and the TxSize statistics show the size of the voice
packets that are being used in a conversation between this ATA 187
and the other device. The values of these statistics should match.
Gaps in voice calls 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.
Table 6-2 ATA 187 Troubleshooting (continued)
Summary Explanation