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Cisco Unified IP Phone 7960G/7940G Administration Guide for Cisco Unified Communications Manager 7.0 (SCCP)
OL-15498-01
Chapter 8 Troubleshooting and Maintenance
General Troubleshooting Tips
General Troubleshooting Tips
Table 8-2 provides general troubleshooting information for the Cisco Unified IP Phone.
Ta b l e 8-2 Cisco Unified IP Phone Troubleshooting
Summary Explanation
Connecting a Cisco Unified IP Phone
to another Cisco Unified IP Phone/
Cisco does not support connecting an IP phone to another IP phone through the PC
port. Each IP phone should directly connect to a switch port. If phones are connected
together in a line (by using the PC port), the phones will not work.
Poor quality when calling digital
mobile phones using the G.729
protocol.
In Cisco Unified Communications Manager, you can configure the network to use the
G.729 protocol (the default is G.711). When using G.729, calls between an IP phone
and a digital mobile phone will have poor voice quality. Use G.729 only when
absolutely necessary.
Prolonged broadcast storms cause
IP
phones to re-register.
Prolonged broadcast storms (lasting several minutes) on the voice VLAN cause the IP
phones to re-register with another Cisco Unified Communications Manager server.
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 telephone
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. See the
“Unlocking and Locking
Options” section on page 4-2 for details.
Phone resetting. 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.
LCD display issues. If the display appears to have rolling lines or a wavy pattern, it might be interacting
with certain types of older fluorescent lights in the building. Moving the phone away
from the lights, or replacing the lights, should resolve the problem.
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 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 the “Call Statistics Screen” section on page 6-10 for information about displaying
these statistics.