Solution
If the phone continues to reset, eliminate DNS or other connectivity errors by following the procedure in
Determine DNS or connectivity issues, on page 284
.
Power Connection Problems
Problem
The phone does not appear to be powered up.
Solution
In most cases, a phone restarts 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 connects to an external power
supply.
Physical Connection Problems
Problem
The physical connection to the LAN may be broken.
Solution
Verify that the Ethernet connection to which the Cisco Unified IP Phone connects is up. For example, check
whether the particular port or switch to which the phone connects is down and that the switch is not rebooting.
Also ensure that no cable breaks exist.
Cisco Unified IP Phone Security Problems
The following sections provide troubleshooting information for the security features on the Cisco Unified IP
Phone. For information about the solutions for any of these issues, and for additional troubleshooting
information about security, see
Cisco Unified Communications Manager Security Guide
.
CTL File Problems
The following sections describe problems with the CTL file.
Authentication Error, Phone Cannot Authenticate CTL File
Problem
A device authentication error occurs.
Cause
CTL file does not have a Cisco Unified Communications Manager certificate or has an incorrect certificate.
Cisco Unified IP Phone 8961, 9951, and 9971 Administration Guide for Cisco Unified Communications Manager 10.0
(SIP)
273
Troubleshooting and Maintenance
Physical Connection Problems
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