How to set up a virtual machine in brouter mode on Hetzner?

Question

Hetzner

If a dedicated Hetzner server with CentOS (host system) and one additional IP. Requires the Debian VM to be visible to the internet at this sub-IP in routed(brouter/routed bridge) mode.
The following is done - using libvirt installed VM Debian (guest system).
In accordance with the instructions
, the settings are made on the host and guest systems. As a result, guest does not respond to host.
After that, the netmask 255.255.255.255 on the guest was changed to 255.255.255.192 and the guest became visible from the host system. But all the same, only host is visible from the Internet, guest again does not respond.
Advise where else to look for the correct setting in 'Routed' mode. Tutorials for the Bridge mode come across everywhere.