Hi mayijie, indeed from your latest systemd-networkd debug log it looks like the enc1000.1300 vlan interface was created successfully, I wonder why it doesn't show up in your "ip link" output..


What I find interesting, though it that the enc1000 interface seems to come UP during boot, but then looses carrier briefly (cable disconnected? underlying VM reconfigured?), which interrupts the creation of the enc1000.1300 vlan.

Would you mind adding the "ignore-carrier: true" setting to your enc1000 Netplan configuration and check if this makes any difference?

Here's the relevant log where carrier is lost:
```
Jun 19 03:00:33 a90ubut15 systemd-networkd[964]: enc1000: Flags change: +UP +LOWER_UP +RUNNING
Jun 19 03:00:33 a90ubut15 systemd-networkd[964]: enc1000: Link UP
Jun 19 03:00:33 a90ubut15 systemd-networkd[964]: enc1000: Gained carrier
Jun 19 03:00:33 a90ubut15 systemd-networkd[964]: enc1000: found matching network '/run/systemd/network/10-netplan-enc1000.network'.
Jun 19 03:00:33 a90ubut15 systemd-networkd[964]: enc1000: LLDP Rx: Started LLDP client
Jun 19 03:00:33 a90ubut15 systemd-networkd[964]: enc1000: link_check_ready(): link is not activated.
Jun 19 03:00:33 a90ubut15 systemd-networkd[964]: enc1000: link_check_ready(): link is not activated.
Jun 19 03:00:33 a90ubut15 systemd-networkd[964]: enc1000: link_check_ready(): link is not activated.
Jun 19 03:00:33 a90ubut15 systemd-networkd[964]: enc1000: link_check_ready(): link is not activated.
Jun 19 03:00:33 a90ubut15 systemd-networkd[964]: enc1000: link_check_ready(): link is not activated.
Jun 19 03:00:33 a90ubut15 systemd-networkd[964]: enc1000: link_check_ready(): link is not activated.
Jun 19 03:00:33 a90ubut15 systemd-networkd[964]: enc1000: link_check_ready(): link is not activated.
Jun 19 03:00:33 a90ubut15 systemd-networkd[964]: enc1000: link_check_ready(): link is not activated.
Jun 19 03:00:33 a90ubut15 systemd-networkd[964]: enc1000: link_check_ready(): link is not activated.
Jun 19 03:00:33 a90ubut15 systemd-networkd[964]: enc1000: Received new foreign route (configured): dst: ff00::/8, src: n/a, gw: n/a, prefsrc: n/a, scope: global, table: local(255), proto: kernel, type: multicast, nexthop: 0, priority: 256, flags: n/a
Jun 19 03:00:33 a90ubut15 systemd-networkd[964]: enc1000: Received new foreign route (configured): dst: fe80::/64, src: n/a, gw: n/a, prefsrc: n/a, scope: global, table: main(254), proto: kernel, type: unicast, nexthop: 0, priority: 256, flags: n/a
Jun 19 03:00:33 a90ubut15 systemd-networkd[964]: enc1000: link_check_ready(): stacked netdevs are not created.
Jun 19 03:00:34 a90ubut15 systemd-networkd[964]: enc1000.1300: Creating
Jun 19 03:00:34 a90ubut15 systemd-networkd[964]: enc1000: Flags change: -UP -LOWER_UP -RUNNING
Jun 19 03:00:34 a90ubut15 systemd-networkd[964]: enc1000: Link DOWN
Jun 19 03:00:34 a90ubut15 systemd-networkd[964]: enc1000: Lost carrier
Jun 19 03:00:34 a90ubut15 systemd-networkd[964]: enc1000: LLDP Rx: Stopping LLDP client
Jun 19 03:00:34 a90ubut15 systemd-networkd[964]: enc1000: Forgetting foreign route (n/a): dst: fe80::/64, src: n/a, gw: n/a, prefsrc: n/a, scope: global, table: main(254), proto: kernel, type: unicast, nexthop: 0, priority: 256, flags: n/a
Jun 19 03:00:34 a90ubut15 systemd-networkd[964]: enc1000.1300: Failed to get link from ifindex 3, ignoring: No such device
Jun 19 03:00:34 a90ubut15 systemd-networkd[964]: enc1000: Forgetting foreign route (n/a): dst: ff00::/8, src: n/a, gw: n/a, prefsrc: n/a, scope: global, table: local(255), proto: kernel, type: multicast, nexthop: 0, priority: 256, flags: n/a
Jun 19 03:00:34 a90ubut15 systemd-networkd[964]: enc1000: Kernel removed unknown foreign address (n/a): fe80::ca:72ff:fe80:acb0/64 (valid forever, preferred forever), flags: tentative,permanent, scope: link
Jun 19 03:00:34 a90ubut15 systemd-networkd[964]: enc1000: Flags change: +UP +LOWER_UP +RUNNING
Jun 19 03:00:34 a90ubut15 systemd-networkd[964]: enc1000: Link UP
Jun 19 03:00:34 a90ubut15 systemd-networkd[964]: enc1000: Gained carrier
Jun 19 03:00:34 a90ubut15 systemd-networkd[964]: enc1000: found matching network '/run/systemd/network/10-netplan-enc1000.network'.
```