I have recently started using dropbear-initramfs to try to help with situations
where boot problems need to be resolved remotely.

I have it working on one system but when I try to use it on a second system it doesn't work.
This second system is a server which is connected directly to a VLAN trunk, so the IP config
needs to specify a VLAN to use.

I tried using the kernel command line "ip=" to specify the interface name with a VLAN id
in the same format as used in /etc/network/interfaces:

ip=192.168.0.205::::name.a.b.c:eth0.100::192.168.0.1:

However, this did not work.

It would be great if I could use dropbear-initramfs on the host systems
which are directly connected to the VLAN trunk.

Control: reassign -1 initramfs-tools-core

The network configuration routine isn't implemented in src:dropbear but in
initramfs-tools-core's /usr/share/initramfs-tools/scripts/functions:configure_networking().
All dropbear-initramfs does is to call that function in its hook script.

AFAICT initramfs-tools=0.140ubuntu14 adds vlan (and IPv6) support but I
don't know if these patches are viable for Debian.

A solution would be really great, because ...

... crypted root and vlan (in combination) are not uncommon.

... all other (large) distributions (Ubuntu, RedHat, SuSe) already
supports this.

With many thanks in advance,
Thomas