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Cisco Unified IP Phone 8961, 9951, and 9971 Administration Guide for Cisco Unified Communications Manager 8.5 (SIP)
OL-20861-01
Chapter 12 Troubleshooting and Maintenance
Cisco Unified IP Phone Resets Unexpectedly
Eliminating DNS or Other Connectivity Errors
If the phone continues to reset, follow these steps to eliminate DNS or other connectivity errors:
Procedure
Step 1 Use the Reset Settings menu to reset phone settings to their default values. See the “Resetting the Cisco
Unified IP Phone” section on page 12-15 for details.
Step 2 Modify DHCP and IP settings:
a. Disable DHCP. See the “Ethernet Setup Menu” section on page 7-4 for instructions.
b. Assign static IP values to the phone. See the “Ethernet Setup Menu” section on page 7-4 for
instructions. Use the same default router setting used for other functioning Cisco Unified IP Phones.
c. Assign a TFTP server. See the “Ethernet Setup Menu” section on page 7-4 for instructions. Use the
same TFTP server used for other functioning Cisco Unified IP Phones.
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
“Determining the MAC Address for a Cisco Unified IP Phone” section on
page 2-13.
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.