General Troubleshooting Tips - Cisco 7970G Administration Manual

Chapter 9 Troubleshooting and Maintenance

General Troubleshooting Tips

Table 9-2 Cisco Unified IP Phone Troubleshooting
Summary
Daisy-chaining IP phones
Poor quality when calling digital cell
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
Cisco Unified IP Phone Administration Guide for Cisco Unified CallManager 5.1 (SIP), Cisco Unified IP Phones
OL-11524-01
Table 9-2 provides general troubleshooting information for the Cisco Unified IP
Phone.
Explanation
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.
In Cisco Unified CallManager, 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.
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'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.
General Troubleshooting Tips
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