Example 10. of man page of systemd.network(5) shows:
```
Example 10. MacVTap
This brings up a network interface "macvtap-test" and attaches it to "enp0s25".
# /usr/lib/systemd/network/25-macvtap.network
[Match]
Name=enp0s25
[Network]
MACVTAP=macvtap-test
```
Which is a MACVTAP example and is currently unsupported in NixOS.
This is useful for people using "modern" technologies with virtual machines.
This essentially backports
https://github.com/systemd/systemd/pull/27791. `systemd-networkd.service`
is sent the `SIGTERM` signal, but it is not required to be stopped
before `initrd-switch-root.target` is reached, despite the use of
`systemctl isolate initrd-switch-root.target`. This is because when
there is no ordering at all between two units, and a transaction stops
one and starts the other, the two operations can happen
simultaneously. This means the service could still be running when
`switch-root` actually occurs. Then, stage 2 systemd will see the
service still running and decide it doesn't need to add a start
operation for it to its initial transaction. Finally, the service
exits, but only after it's already too late. If, however, there is any
ordering at all between a stopping unit and a starting unit, then the
stop operation will be done first. This way, we ensure that the
service is properly exited before doing `switch-root`.
This is something to keep in mind going forward. There may be other
services that need this treatment. These `before` and `conflicts`
definitions are the correct way to ensure a unit is actually stopped
before you reach initrd-switch-root
The `B` in bridge should be capitalized.
It currently leads to an evuluation error:
```
error: attribute 'sectionbridgeVLAN' missing
at /nix/store/7wmrwj0sgwg1iivxk43lpkqjhji57mq7-source/nixos/modules/system/boot/networkd.nix:2386:56:
2385| example = { VLAN = "10-20"; };
2386| type = types.addCheck (types.attrsOf unitOption) check.network.sectionbridgeVLAN;
| ^
2387| description = lib.mdDoc ''
Did you mean sectionBridgeVLAN?
```
