Specifications

9-11
Cisco Unified IP Phone 7906G and 7911G for Cisco Unified Communications Manager 8.0
OL-21033-01
Chapter 9 Troubleshooting and Maintenance
General Troubleshooting Tips
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.
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.
Peer to peer image distribution
fails.
If the peer to peer image distribution fails, the phone will default to using the TFTP server
to download firmware. Access the log messages stored on the remote logging machine to
help debug the peer to peer image distribution feature.
Note These log messages are different than the log messages sent to the
phone log.
Cisco VT Advantage/Unified
Video Advantage (CVTA)
If you are having problems getting CVTA to work, make sure that the PC Port is enabled,
and that CDP is enabled on the PC port. See Network Configuration Menu, page 4-5.
(applies to 7911G only)
Table 9-2 Cisco Unified IP Phone Troubleshooting (continued)
Summary Explanation