Cisco 7975G - General Troubleshooting Tips

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Cisco Unified IP Phone 7975G Administration Guide for Cisco Unified Communications Manager 6.0
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Chapter 9 Troubleshooting and Maintenance
General Troubleshooting Tips
General Troubleshooting Tips
Table 9-2 provides general troubleshooting information for the Cisco Unified IP Phone.
Table 9-2 Cisco Unified IP Phone Troubleshooting
Summary Explanation
Daisy-chaining IP
phones
Daisy chaining (connecting an IP phone to another
IP phone through the access port) is not supported.
Each IP phone should directly connect to a switch
port.
Poor quality when
calling digital cell
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 cellular phone will have
poor voice quality. Use G.729 only when absolutely
necessary.
Prolonged broadcast
storms cause IP 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 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.
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 4-3 for details.
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.