hostonly network should allow all valid Private IPv4 ranges by default

[jehiah]

From https://www.virtualbox.org/manual/ch06.html#network_hostonly

VirtualBox will only allow IP addresses in 192.68.56.0/21 range to be assigned to host-only adapters. For IPv6 only link-local addresses are allowed.

By default VirtualBox should allow IPv4 ranges in all ​RFC 1918 Private IP ranges including

• 10.0.0.0/8
• 172.16.0.0/12
• 192.168.0.0/16

This restriction (new in 6.1.28) was a breaking change for users using valid private IP addresses outside of 192.68.56.0/21.

[jehiah]

Related tickets which I found helpful in tracking this down.

• #20626 describes the error users encounter w/ IP addresses outside of this range and the way to configure it
• ​vagrant#12564 updates vagrant to validate IP ranges
• ​vagrant#12557 vagrant support thread including challenges a number of users had w/ IP range restrictions

[Klaus Espenlaub]

Yes, it is (intentionally) a breaking change, and your proposal is putting networks in normal user's hands which can cause trouble.

The basic problem is visible in simple networks. In more or less every private VirtualBox user's network there is an Internet router, which puts all devices in the LAN in some 192.168.x.0/24 network.

If the user picks this network as a host-only network then "bad things will happen".

Unfortunately it isn't possible to detect which network(s) will be causing problems (especially not in setups which are involving 2 or more LAN segments), and therefore the administrator will have to decide.