On Ubuntu 20.04, I've define following interface in /etc/network/interfaces:
auto eth0:0
iface eth0:0 inet static
address 192.168.1.3 # my meaningful comment
netmask 255.255.255.0
When I've trying to bring this interface up I've got an error:
# ifup eth0:0
Not enough information: "dev" argument is required.
ifup: failed to bring up eth0:0