How to add a VLAN ID to a network interface?
First check if the the kernel module 8021q is loaded with
$lsmod | grep 8021q
if it is not loaded, load the relative module with
#modprobe 8021q
Then either
vconfig add IF VLAN_ID
or
ip add link IF name IF.VLAN_ID type vlan id VLAN_ID
Where IF is the network card interface: eth0, eth1, ens33, etc.
And VLAN_ID is the ID of your VLAN
For example if the VLAN ID is 5 and the ethernet interface is eth1, you can either run
#vconfig add eth1 50
or
#ip add link eth1 name eth1.5 type vlan id 5
You must be root or have the appropriate root permissions.