Voice VLAN command - LLDP seems to stop working

FWIW this issue seems to be fixed. Originally the config was 

interface 1/0/1

voice vlan 10

switchport mode access

switchport access vlan 20

But the switch would randomly stop passing the tagged VLAN traffic. I changed the config to:

interface 1/0/1

voice vlan 10

switchport mode trunk

switchport trunk native vlan 20

switchport trunk allowed vlan 10,20

I haven't had a single DHCP failure/VLAN tag drop since moving to this config.

This behavior seems to only occur on the M4300 series - the M4100 actually rejects switchport mode access as a valid option when using voice VLAN (I have those access ports configured in general mode but I'll be updating them later for the sake of consistency). Maybe it would be nice in future updates to prompt users to use a trunk config when enabling voice VLAN on switchports so they don't spend their time flailing about like I did (this problem lasted for like, seven or eight months!). :)

To be clear, it wasn't LLDP failing to maintain the voice VLAN tag, it was the switch refusing to pass tagged traffic and the phone dropping the VLAN tag after DHCP repeatedly failed (which is normal Mitel/Shoretel behavior).

If anyone else googles this problem hopefully they find this post. :) :womanvery-happy: