hildred's questions

So in a general case 802.1q is handy and cool, grab two switches connect them with a single cable, do some configuration and have multiple virtual lans spanning both switches. You can even do funky stuff like have an ip phone have a switch in it allowing the local computer port to be on a separate vlan from the phone over one cable.

And linux can easily be setup with virtual ethernet cards so that that one cable between your linux box and the switch can be multiple networks. And with virtual switches and virtual machines you can configure it just like you would a real switch and real machines with less wire. All useful.

But I am confused by microsoft's implementation. (I know that there are aftermarket network drivers that present multiple network cards, but these are not default.) You can configure which vlan the network card uses. As in only one. What advantage does this provide? if you cannot support multiple vlans all that tagging does is make each packet a little larger for no reason. The only use cases I can think of is for with unmanaged switches or hubs to be segmented (which I might try in a lab, just to see if I can, but not something I would use in production), or to deal with a misconfigured switch (although fixing the switch might be a better idea).

What have you used it for?

So here is the challenge, take one computer (named host) running windows with virtualbox and more than one network card and the same number of administratively separated subnets. Add a policy requirement that the windows box must have an ip address on one and only one subnet and that the guest must have an ip address, but it must not be on the subnet that the host is on. bridged networking is prefered as running vpn to the guest across the host's network is real overkill given that the wire is right there.

The naive solution (does not work) would be to configure an ip address on the first network card (static or dhcp as normal) and disable the ip binding on the second network card. Then when configuring the virtual machine, to select bridged networking and the second network adaptor. This utterly fails as bridged networking only lists network cards that are bound to ip (either 4 or 6, both also works fine, it may work with ipx or netbeui but they are not available for recent versions of windows).

A workaround is to enable an ip protocol on the second adaptor and misconfigure it so that the address it uses is on a subnet that is not reachable, but the second shift sysop keeps trying to fix it.

Is there a better solution?