General Troubleshooting Tips - Cisco 7931G Administration Manual

General Troubleshooting Tips

General Troubleshooting Tips
Table 9-2
Table 9-2 Cisco Unified IP Phone Troubleshooting
Summary
Daisy-chaining IP phones
Poor quality when calling digital
mobile phones using the G.729
protocol
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
Display issues
Dual-Tone Multi-Frequency
(DTMF) delay
Codec mismatch between the phone
and another device
Sound sample mismatch between the
phone and another device
Cisco Unified IP Phone 7931G Administration Guide for Cisco Unified Communications Manager 8.0 (SCCP and SIP)
9-10
provides general troubleshooting information for the Cisco Unified IP Phone.
Explanation
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 (daisy chaining by using the PC port), the phones will not work.
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.
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.
Caution The computer 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.
By default, the network configuration options are locked to prevent users from making
changes that could affect their network connectivity. You must unlock the network
configuration options before you can configure them. For details, see
Locking Options, page
If the display appears to have rolling lines or a wavy pattern, it may be interacting with
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 may not be recognized.
The RxType and the TxType statistics show the codec that is being used for a
conversation between this Cisco Unified 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 a transcoder is in place to handle the service.
For information about displaying these statistics, see
The RxSize and the TxSize statistics show the size of the voice packets that are being
used in a conversation between this Cisco Unified IP Phone and the other device. The
values of these statistics should match.
For information about displaying these statistics, see
Chapter 9
4-3.
Troubleshooting and Maintenance
Unlocking and
Call Statistics Screen, page
Call Statistics Screen, page
OL-20798-01
7-12.
7-12.