Cisco 7941G - Unified IP Phone VoIP Administration Manual page 243

Chapter 9 Troubleshooting and Maintenance
Table 9-2 Cisco Unified IP Phone Troubleshooting (continued)
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.
Phone resetting.
LCD display issues.
Dual-Tone Multi-Frequency (DTMF)
delay.
Cisco Unified IP Phone 7961G/7961G-GE and 7941G/7941G-GE for Cisco Unified Communications Manager 6.1
OL-14620-01
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's network connection and plug the cable into a desktop
computer.
The computer's network card cannot receive power
Caution
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.
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 4-3
details.
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.
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.
When you are on a call that requires keypad input, if you press
the keys too quickly, some of them might not be recognized.
General Troubleshooting Tips
for
9-15