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Cisco Unified IP Phone 6901 and 6911 Administration Guide for Cisco Unified Communications Manager 8.5 (SCCP and SIP)
OL-23874-01
Chapter 7 Troubleshooting and Maintenance
General Troubleshooting Tips
Step 3 On the Cisco Unified Communications Manager server, verify that the local host files have the correct
Cisco
Unified Communications Manager server name mapped to the correct IP address.
Step 4 From Cisco Unified Communications Manager, choose System > Server and verify that the server is
referred to by its IP address and not by its DNS name.
Step 5 From Cisco Unified Communications Manager, choose Device > Phone > Find and verify that you have
assigned the correct MAC address to this Cisco
Unified IP Phone. For information about determining a
MAC address, see the
“Using Cisco Unified IP Phones with Different Protocols” section on page 2-11.
Step 6 Power cycle the phone.
Checking Power Connection
In most cases, a phone will restart if it powers up by using external power but loses that connection and
switches to PoE. Similarly, a phone may restart if it powers up by using PoE and then gets connected to
an external power supply.
General Troubleshooting Tips
Table 7-1 provides general troubleshooting information for the Cisco Unified IP Phone.
Ta b l e 7-1 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 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.