This is not my article I copy and pasted if from the below. The only reason it’s on here is because it took me a while to find so I figured I would put it here since it’s useful to me.
by lunarg on February 20th 2017, at 14:53
When provisioning non-Cisco phones on a Cisco-switched network, you may notice that the configured voice VLAN is not correctly provisioned to the phone. The phone ends up in the data VLAN, rather than the voice VLAN even though the switch port has been correctly configured.
There are two protocols which can be used to provision the correct VLAN to your phones: Cisco Discovery Protocol (CDP) and Link-Layer Discovery Protocol (LLDP). CDP is a proprietary protocol and is only supported on Cisco-switches and Cisco-phones. Non-Cisco devices usually use LLDP, which is an open standard supported by most other vendors. Although Cisco switches also support LLDP, it is by default not enabled, resulting in the phones not being provisioned correctly. In order to enable LLDP and allow voice VLAN provisioning, you need to configure the ports correctly (similar when using Cisco-phones) and enable LLDP to allow the phones to get the correct VLAN tag for voice VLAN.
To enable LLDP:
# configure terminal
(conf)# lldp run