we are located in rz 6 which still allows some subnets to be used by two machines on virtual interfaces. our latest subnet which we registered though doesn't route to both machines any more.
did you get any feedback from hetzner? the support simply told me via e-mail that ha-solutions aren't supported any more and theres no alternative.
i read that virtual mac-addresses could do the job? maybe we could even fake the mac by the active machine to bypass that check. did anyone of you guys get information obout alternatives?