Specifications

9-10
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
General Troubleshooting Tips
This section provides troubleshooting information for some common issues that might occur on the
Cisco Unified IP Phone.
Table 9-2 provides general troubleshooting information for the Cisco Unified IP Phone.
Phone cannot obtain a
DHCP-assigned IP address.
These errors typically indicate that the phone completed a factory reset (see Performing
a Factory Reset, page 9-13) while 802.1X was enabled. A factory reset deletes the
shared secret, which is required for 802.1X authentication and network access. To
resolve this issue, you have two options:
• Temporarily disable 802.1X on the switch
• Temporarily move the phone to a network environment that is not using 802.1X
authentication
When the phone starts up normally in one of these conditions, you can access the
802.1X configuration menus and re-enter the shared secret (see 802.1X Authentication
and Status, page 4-37).
Phone does not register with
Cisco Unified Communications
Manager.
Phone status display as
“Configuring IP” or “Registering.”
Cannot access phone menus to
verify 802.1X status.
Table 9-1 Cisco Unified IP Phone Security Troubleshooting (continued)
Problem Possible Cause
Table 9-2 Cisco Unified IP Phone Troubleshooting
Summary Explanation
Daisy-chaining IP phones. 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.
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 re-register.
Prolonged broadcast storms (lasting several minutes) on the voice VLAN cause the IP
phones to re-register with another Cisco Unified Communications Manager server.
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 Unlocking and Locking Options,
page 4-3 for details.