24.3 Virtual Machine Networking

Virtual machines will invariably need to be connected to a network to be of any practical use. One option is for the guest to be connected to a virtual network running within the operating system of the host computer. In this configuration any virtual machines on the virtual network can see each other but access to the external network is provided by Network Address Translation (NAT). When using the virtual network and NAT, each virtual machine is represented on the external network (the network to which the host is connected) using the IP address of the host system. This is the default behavior for KVM virtualization on Ubuntu and generally requires no additional configuration. Typically, a single virtual network is created by default, represented by the name default and the device virbr0.

In order for guests to appear as individual and independent systems on the external network (i.e. with their own IP addresses), they must be configured to share...