Virtualbox on multiple computers breaks name resolution

[B Lloyd]

When installing virtualbox on multiple computers, a name lookup from a command such as "ping HISCOMPUTER" will start to fail on an ad-hoc (home) style network.

The problem is that when doing a name lookup, the computer broadcasts a search for the name. When it recieves a response from the other computer, the response includes all addresses for the machine. 192.168.56.1 is used by VirtualBox for the Host Network only adapter. Both computers will thus have an address of 192.168.56.1. A hop to your own address will always be the cheapest, so the name resolves to the 192.168.56.1. Thus the computers stop talking.

This is a problem with how networking works, but is exacerbated by the virtual networking component. The only solution I can see is to not use the same address for the two disconnected networks. Changing the address pool in one of them does fix the problem. However, Virtualbox in a fresh install shouldn't break existing networking.

This affects 2.X, 3.X, and 4.X clients. You don't even need to have a guest running to experience this.

[B Lloyd]

The only way I can see fixing is is to add some smarts to the networking installer. When installing a network either always use a random IP of 192.168.Y.1, where Y is 56-99. To add even more networks, you could check existing networks that are connected and if 10.X isn't in use create a subnet from that address space instead which gives you 65000 subnets to randomize over. Very unlikely to hit a collision in that case.

An after the fact fixup could be to monitor name resolutions and when another computer returns an IP address of a virtual network that isn't responding on that network, note it and prompt the user to re-randomize the virtualbox network (either immediately or when next virtualbox is run).

[aeichner]

Please reopen if still relevant with a recent VirtualBox release.