Core Issue
Cisco Discovery Protocol (CDP) is a device-discovery protocol that runs on all Cisco-manufactured equipment. Using CDP, a device can advertise its existence to other devices and receive information about other devices in the network.
The Cisco IP phone uses CDP to communicate information such as auxiliary VLAN ID, per port power management details, and Quality of Service (QoS) configuration information with the Cisco Catalyst switch.
Resolution
Power the phone off, then on again to clear all previous files.
The log shown below is an example of the kind of data that is displayed:
Configuration:
interface FastEthernet0/1
switchport trunk encapsulation dot1q
switchport mode trunk
switchport voice vlan 77
spanning-tree portfast
Log:
5: PORT_UP Event for port 0
7: PORT_UP Event for port 1
43: Sending Trigger 2 on port 1
43: Sending Trigger 2 on port 0
43: Received VVLan 77 VLan 1 on port 65535
143: Sending Trigger 2 on port 0
143: Sending Trigger 2 on port 1
143: Received VVLan 77 VLan 1 ttl 180 on port 0 from Sweety
143: Start Synch port 0
507: Wait Timer expired on port 1
507: Start Synch port 1
643: End Synch port 0
1007: End Synch port 1
1007: Best VLANs: 77, -4096
1007: Selecting port 0, VVLAN 77 VLAN 1 ttl 177
1007: Notify configure changes with VVLAN 77
