Comment 0 for bug 1743200

In the old /etc/network/interfaces I could define a virtual interface:

    auto eth0
    iface eth0 inet static
        address aaa.aaa.aaa.aaa
        netmask 255.255.255.0
        gateway aaa.aaa.aaa.1

    auto eth0:0
    iface enp7s0f0:0 inet static
        address bbb.bbb.bbb.bbb
        netmask 255.255.255.0

This is not possible to achieve with the netplan. The only exisiting posibilities are either to create a VLAN, which may be not an option in some networks where you have no access to other hosts, or to define both addresses for one interface:

    network:
      version: 2
      renderer: networkd
      ethernets:
        eth0:
          addresses: [aaa.aaa.aaa.aaa/24, bbb.bbb.bbb/24]
          gateway4: aaa.aaa.aaa.1

This solution is not optimal either, because configuring iptables or some services may require specific interface name for a single network.

It should be possible to add the same physical interfaces with different networks and different alias names.