Confusion about voice vlan

The main reason why I decide to create posts like this one despite the fact that there are millions if not more similar posts, explanations and websites out there on the internet is mainly because I simply enjoy gathering all relevant information from various sources then combine it all into a single unit so we do not have to jump from one website to another in order to find whatever we’re after, this relates to Cisco and Cisco only of course
This set up is most definitely how it all looks like in your office environment, go ahead and first check and see how your PC connects with your desk phone then from the phone trace the cable which most likely connects to RJ45 floor port which most likely is located under your desk then it all goes through the walls of your company all the way back to your Company’s Comms Room (Data Centre) where it connects into a patch panel in one of the network cabinets and from there directly to L2 switch which then goes to your business’s L3 Core switches, routers,firewalls etc …


I have spent really long hours on this one, especially the one that involves  802.1p tag
I have been looking into this like a madman and must admit that Voice combined with QOS is not the easiest to understand.
The reason why it takes so long top prepare for the LAB is because you never know what Cisco is going to ask you to configure or troubleshoot and this is because we need to know and understand it all !!
The upstream switch communicates with the Cisco IP phone using CDP to set up an interconnection link that allows the Cisco IP phone to send VoIP packets on its uplink port back to the switch, either in the VoIP VLAN or in the data VLAN
So there are 4 modes to set up a switch port you expect to plug a phone into (Interface Ethernet 4/0 connects to the phone)
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1. First you can just use a regular access port. In this mode, both the phone traffic and pc data both land on the same access vlan and there is no way to distinguish between the two. Two things to note, because the traffic will use the same vlan then you have a security risk as well as having no ability to provide QOS priority to only the phone. Any QOS is applied to ALL traffic coming in that switch port.
Rack5SW2(config)#int ethernet 4/0
Rack5SW2(config-if)#switchport mode access
Rack5SW2(config-if)#switchport access vlan 79
or
Rack5SW2(config)#int ethernet 4/0
Rack5SW2(config-if)#switchport mode access
Rack5SW2(config-if)#switchport voice vlan none