Chapter9 Troubleshooting and Maintenance
General Troubleshooting Tips
9-14
Cisco Unified IP Phone 7906G and 7911G Administration Guide for Cisco Unified CallManager
OL-10008-01
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 page4-3 for
details.
Phone resetting. The phone resets when it loses contact with the
Cisco Unified CallManager 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.
Loopback condition. A loopback condition can occur when the following conditions
are met:
•The SW Port Configuration option in the Network
Configuration 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, re-enable the port from the switch.
Table9-2 Cisco Unified IP Phone Troubleshooting (continued)
Summary Explanation