I just wanted to jump in and reply with a thank you as well for your post. There’s a couple of other details people may want to consider if they are following this. Hopefully “future me” also finds this helpful.
The parent interface configuration:
It is likely that if you are using VLANs that you don’t want your host sending untagged traffic, or basically doing anything on the untagged interface at all. This can be achieved by setting the parent interface to not autoconnect on boot. I did this with the following commands:
nmcli con edit Supervisor\ eth0
set connection.autoconnect no
save
quit
This has the effect that the “Supervisor eth0” connection will show as down when you do a nmcli con show but the VLAN sub interfaces will remain operational.
Note: it is not sufficient to just delete the “Supervisor eth0” connection, HA will automatically recreate it on reboot with default settings including autoconnect enabled.
Route Metrics:
If you want to control routing so that your preferred network is used as your default route, you can set the route metrics on your non-preferred networks to a high value. For example, I run two IOT VLANs, one which does not have Internet access (VLAN 100), and one that does (VLAN 101), plus I have a management/system network (VLAN 1) with Internet access. I want HA to use VLAN 1 as its default route. If all route metrics are equal, HA may just decide to use VLAN 101 for its preferred default route which I don’t want. To fix this I used the following commands:
nmcli con edit eth0@vlan100
set ipv4.route-metric 2000
set ipv6.route-metric 2000
save
quit
nmcli con edit eth0@vlan101
set ipv4.route-metric 2000
set ipv6.route-metric 2000
save
quit
All my interfaces use DHCP configuration (and DHCP reservations on my router), and the route metrics on routes advertised through my eth0.1 interface get a metric value of 400 (as set by HA). Setting the other interfaces to use a metric of 2000 means the eth0.1 interface routes are preferred (lowest metric number wins).