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Cisco Unified IP Phone 7970G/7971G-GE Administration Guide for Cisco Unified Communications Manager 7.0
OL-15299-01
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 (see the “Performing a
Factory Reset” section on page 9-14) 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 authentication on
the switch.
• Temporarily move the phone to a network
environment that is not using 802.1X
authentication.
Once 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 the “802.1X Authentication and Status”
section on page 4-31).
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 (by using the
PC port), the phones will not work.
Poor quality when calling mobile
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 mobile 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.