Linux in a Nutshell, 6th Edition

Configuring Networks

Your basic network options are to use bridging or Network Address Translation (NAT). In bridging, a special bridge interface transparently connects your virtual interfaces to your host’s physical interface(s). Your virtual servers will share the physical interface.

Using NAT, your virtual servers are assigned private network IP addresses, and another interface then provides the NAT for your system. This NAT interface is essentially a bridge as well. A bridge is really any interface used to hook your virtual interfaces up to your physical interfaces. Still, these two approaches are commonly referred to as bridging and NAT.

VMware uses a third option. It creates a virtual switch to which you connect your guests’ interfaces. The default switch, however, simply bridges the switch to the server’s network interface card. Neither Xen or KVM come with a ready-made virtual switch solution, although some vendors may offer virtual switch solutions you could add to your system.

Upon installation of the hypervisor and libvirt, most distributions will automatically configure basic networking support. They will likely configure both a NAT and bridge interface. Xen’s tools will use the bridge interface by default, but virt-manager’s tools will likely use NAT.

The approach you want to use will depend on the kind of system on which you have installed the host operating system. If you are installing on a system that might frequently change networks (for example, a notebook you move ...