The switchport voice vlan command initiates CDP packets which tell the phone to send voice traffic with the correct QoS markings (both layer 2 and 3). It should be there to make sure the phones to talk on the right vlan. Also, because its a switchport )not a trunkport) and if you're using stp or pvst then portfast is automatically input onto that port.
Not entirely, it does not look for frames with a COS marking in them, as you could apply QoS markings to normal PC data traffic. The CoS/IPP/DSCP markings are sent to a Cisco VoIP Phone if one is connected.
The command allows a non-cisco device to send VoIP frames already tagged with the correct 802.1q value, to be switched in the Voice VLAN.
That has nothing to do with it, the physical port is a swicth port, NOT a trunk port.
1) The command tells the switch to "send" the QoS values/VLAN infromation of the voice VLAN to a cisco phone when connected and detected by the switch and the command is configured under the switch port.
2) The command is also used in the cases where the VoIP phones attached is NOT a cisco phone, but you want the switch to understand any frames that have a marking in the priority field in the frame with an inserted 802.1q field, tagged with the voice vlan ID, and should be switched into the voice vlan as the switch port is a normal switch and NOT a trunk.
We are pleased to announce availability of Beta software for 16.6.3. 16.6.3 will be the second rebuild on the 16.6 release train targeted towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are looking for early feedback from custome...