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Cisco Unified IP Phone Administration Guide for Cisco Unified Communications Manager 8.6 (SCCP and SIP)
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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.
Factory Reset Deleted 802.1X Shared Secret
Phone cannot obtain a DHCP-assigned IP
address
These errors typically indicate that the phone has completed a factory reset
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, 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.
After the phone starts up normally in one of these conditions, you can access
the 802.1X configuration menus and re-enter the shared secret.
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
Tab l e 9-2 Cisco Unified IP Phone Troubleshooting
Summary Explanation
Connecting a Cisco Unified IP Phone to
another Cisco Unified IP Phone
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 (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 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 network card in the computer 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 4-2 for details.