So, here’s a q-in-q subinterface. If you just want the single vlan instead of a vlan stack, just leave the second line out and apply the ip address to eno2.123 instead (your interface names may be different, look at “ip link list” to see them)
ip link add name eno2.123 link eno2 type vlan proto 802.1q id 123
ip link add name eno2.123.456 link eno2.123 type vlan proto 802.1q id 456
ip addr add 10.1.2.3/24 dev eno2.123.456