KVM: How to set up a private network between guests and the host

kenneho · 01-16-2010, 03:24 AM

Hi.

I'm running KVM on my Ubuntu box, and would like the host and guests to share a private network that is not attached to Internet (i.e. not the default NAT setup that comes out-of-the box with libvirt).

The default NAT'ed setup works, except that it connects the guests to the internet, and I guess I could simply block internet related traffic in the firewall, but I'm sure there are smarter ways of doing this. Anyone got tips on how to accomplish this?

- kenneho

janoszen · 01-17-2010, 11:19 AM

It's easy. You need to add a second TAP device to your KVM when starting it up, and the bridge the two new TAP devices together. Done!

(It's about the same as plugging in a network cable between the two computers. It works like a hub. If you want a switch, check out the vde_switch, which has configurable VLAN-s for more sofisticated setups. It's for testing only though, not for a production system.)