I have a basic setup with what is essentially a bridged host-only network on 192.168.56.0/24.
I've got 5 Windows servers on that network.
192.168.56.10
192.168.56.11
192.168.56.12
192.168.56.22
192.168.56.23
I can ping them all from the proxmox host.
They can all ping each other.
I've got one...