There are two scenarios: Applying to VM the first time, on subsequent boots.
On first boot without the updated netplan config, when you first add it
root@ubuntu:/home/ubuntu# ip a 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000 link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 inet 127.0.0.1/8 scope host lo valid_lft forever preferred_lft forever inet6 ::1/128 scope host valid_lft forever preferred_lft forever 2: eth2-2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000 link/ether b8:38:61:bc:60:f6 brd ff:ff:ff:ff:ff:ff 3: ens5: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000 link/ether 52:54:00:ef:88:a2 brd ff:ff:ff:ff:ff:ff inet 10.0.2.15/24 brd 10.0.2.255 scope global dynamic ens5 valid_lft 86177sec preferred_lft 86177sec inet6 fe80::5054:ff:feef:88a2/64 scope link valid_lft forever preferred_lft forever
After a reboot initially the addresses are assigned. root@ubuntu:/home/ubuntu# ip a 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000 link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 inet 127.0.0.1/8 scope host lo valid_lft forever preferred_lft forever inet6 ::1/128 scope host valid_lft forever preferred_lft forever 2: eth2-2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000 link/ether b8:38:61:bc:60:f6 brd ff:ff:ff:ff:ff:ff inet 6.1.6.1/24 brd 6.1.6.255 scope global eth2-2 valid_lft forever preferred_lft forever inet6 2006:1:6::1/116 scope global dadfailed tentative valid_lft forever preferred_lft forever inet6 fe80::ba38:61ff:febc:60f6/64 scope link valid_lft forever preferred_lft forever 3: ens5: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000 link/ether 52:54:00:ef:88:a2 brd ff:ff:ff:ff:ff:ff inet 10.0.2.15/24 brd 10.0.2.255 scope global dynamic ens5 valid_lft 85262sec preferred_lft 85262sec inet6 fe80::5054:ff:feef:88a2/64 scope link valid_lft forever preferred_lft forever
However, if the addresses are cleared from the interface, networkd cannot reapply the config and leaves the interface unconfigured
There are two scenarios: Applying to VM the first time, on subsequent boots.
On first boot without the updated netplan config, when you first add it
root@ubuntu: /home/ubuntu# ip a UP,LOWER_ UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000 MULTICAST, UP,LOWER_ UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000 MULTICAST, UP,LOWER_ UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000 ff:feef: 88a2/64 scope link
1: lo: <LOOPBACK,
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: eth2-2: <BROADCAST,
link/ether b8:38:61:bc:60:f6 brd ff:ff:ff:ff:ff:ff
3: ens5: <BROADCAST,
link/ether 52:54:00:ef:88:a2 brd ff:ff:ff:ff:ff:ff
inet 10.0.2.15/24 brd 10.0.2.255 scope global dynamic ens5
valid_lft 86177sec preferred_lft 86177sec
inet6 fe80::5054:
valid_lft forever preferred_lft forever
After a reboot initially the addresses are assigned. /home/ubuntu# ip a UP,LOWER_ UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000 MULTICAST, UP,LOWER_ UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000 61ff:febc: 60f6/64 scope link MULTICAST, UP,LOWER_ UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000 ff:feef: 88a2/64 scope link
root@ubuntu:
1: lo: <LOOPBACK,
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: eth2-2: <BROADCAST,
link/ether b8:38:61:bc:60:f6 brd ff:ff:ff:ff:ff:ff
inet 6.1.6.1/24 brd 6.1.6.255 scope global eth2-2
valid_lft forever preferred_lft forever
inet6 2006:1:6::1/116 scope global dadfailed tentative
valid_lft forever preferred_lft forever
inet6 fe80::ba38:
valid_lft forever preferred_lft forever
3: ens5: <BROADCAST,
link/ether 52:54:00:ef:88:a2 brd ff:ff:ff:ff:ff:ff
inet 10.0.2.15/24 brd 10.0.2.255 scope global dynamic ens5
valid_lft 85262sec preferred_lft 85262sec
inet6 fe80::5054:
valid_lft forever preferred_lft forever
However, if the addresses are cleared from the interface, networkd cannot
reapply the config and leaves the interface unconfigured
root@ubuntu: /home/ubuntu# ip a UP,LOWER_ UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000 MULTICAST, UP,LOWER_ UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000 MULTICAST, UP,LOWER_ UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000 ff:feef: 88a2/64 scope link
1: lo: <LOOPBACK,
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: eth2-2: <BROADCAST,
link/ether b8:38:61:bc:60:f6 brd ff:ff:ff:ff:ff:ff
3: ens5: <BROADCAST,
link/ether 52:54:00:ef:88:a2 brd ff:ff:ff:ff:ff:ff
inet 10.0.2.15/24 brd 10.0.2.255 scope global dynamic ens5
valid_lft 86177sec preferred_lft 86177sec
inet6 fe80::5054:
valid_lft forever preferred_lft forever