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.
Phone Cannot Connect to LAN
Problem
The physical connection to the LAN may be broken.
Solution
Verify that the Ethernet connection to which the Cisco 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 IP Phone Security Problems
The following sections provide troubleshooting information for the security features on the Cisco 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 troubleshooting 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.
Solution
Install a correct certificate.
Phone Cannot Authenticate CTL File
Problem
Phone cannot authenticate the CTL file.
Cisco IP Phone 8800 Series Administration Guide for Cisco Unified Communications Manager
245
Phone Cannot Connect to LAN
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