Guidelines: Hosting Virtual Machines
For Dedicated Servers acquired before 28-10-2018 and Server Deals
If you want to use a virtualization technique - for example, KVM - on your Dedicated Server, follow these guidelines when configuring the virtual machines.
Please Note
Do not activate the Bridged mode in the virtual machine network settings, select the NAT setting instead. Using the bridged mode will result in your server getting disconnected from the network!
NAT instead of Bridged Mode
In bridged mode, the guest systems get direct access to the network where the host is located. However, unauthorized MAC addresses pose a security risk (MAC spoofing), which is why the identified source - i.e. the host - is immediately disconnected from the network. This means that the server can only be accessed via the serial console and can only be released again by IONOS support.
The scenario described above can be avoided if you use NAT (network address translation). The host acts as a router. Most virtualization solutions use NAT as default setting.
Public IPs
With NAT, network traffic is converted to the address of the host, i.e. the guest is not directly addressable. It is possible to make the guest accessible via his own public IP: For this purpose, IP forwarding must be activated in the host kernel, a route must be created and the desired IP must be entered as Ethernet alias on the guest.