Re: [libvirt-users] Network/bridge questions

On 02/05/2011 01:06 AM, Alex wrote: You're mixing up two different modes of guest network connection: 1) bridge mode - the guest interface definition has <source bridge='xxx'/> (where 'xxx' is the name of a bridge device on the host that has a physical interface directly connected to it). In this case, packets from the guest travel from qemu through a tap device to the bridge (eg "br0") and from there directly out the physical interface. 2) virtual network mode - the guest interface definition has <source network='xxx'/> (where 'xxx' is the name of a virtual network defined in libvirt). The virtual network is in reality a bridge device that has *no connected physical devices*; traffic from the guest will go from qemu through a tap device to the bridge, and from there (possibly be NATed and) be given to the IP routing stack of the host, which will decide which physical interface, if any, to route the packet out. If you are using the first mode, your guest will acquire any dhcp address from the dhcp server on the local physical LAN, and traffic will, as explained above, not be routed through any virtual network created by libvirt. If you want the guest to behave as if it were connected directly to the physical network, use bridged mode. If you want to the guest to be on a separate subnet that lives completely on the host, and only reach the physical network via the IP routing stack of the host, then use one of the virtual network modes. In your question above, you've setup the guest to use bridged mode, but then expect it to behave as if you'd used one of the virtual network modes. If the latter is what you really want, then the XML of the interface definition should look like what I show below, just after your current definition. To connect via libvirt's virtual network (in this case, the network named "default", which operates in NATed mode), change your interface definition as follows: <interface type='network'> <mac address='52:54:00:a8:c5:9d'/> <source network='default'/> <model type='virtio'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/> </interface> See http://www.libvirt.org/formatdomain.html#elementsNICS for a more detailed explanation.