Question : VOIP and CDP

I have an Ethernet cable from a PC connected to a Cisco phone, and the Cisco phone is connected to a Catalyst 6500 series switch. CDP is enabled on the phone. Trunking and two VLAN is configured on the port. How does the switch determine if the packet is coming from the phone or the PC and forward it to the right VLAN?

Answer : VOIP and CDP

If the phone/pc sends a normal network packet then it goes onto whatever VLAN is defined as the native vlan for that port on the switch.
In order to send traffic onto another VLAN the PC or switch needs to send it across the trunk connection which uses 802.1Q tagging where the VLAN number is included within the network packet.