I have a Ubuntu 12.04 LTS machine running KVM/libvirt. It has two physical ethernet interfaces. I have dedicated eth0 as the primary interface and configured bridging on eth1 for my VMs. The KVM host /etc/network/interfaces looks like this:
# The loopback network interface auto lo iface lo inet loopback # The primary network interface auto eth0 iface eth0 inet static address 10.0.5.5 netmask 255.255.255.0 gateway 10.0.5.254 dns-nameservers 10.0.5.1 # The secondary network interface auto br0 iface br0 inet static address 10.0.5.6 netmask 255.255.255.0 gateway 10.0.5.254 bridge_ports eth1 bridge_stp off bridge_fd 0 bridge_maxwait 0
My KVM guests have IP addresses on the 10.0.5.0/24 network. Everything is working as expected.
My question is: if I want to change the network address to a different network altogether, do I simply change it from within the guest OS and then plug my eth1 interface in on the other network...or does the bridging interface need to be reconfigured on the host? If so, how? I am trying to understand the role of the IP assignment on the br0 virtual interface.