Installation guide

Chapter 10. Network Configuration

libvirt adds iptables rules which allow traffic to and from guests attached to the virbr0 device

in the INPUT, FORWARD, OUTPUT and POSTROUTING chains. libvirt then attempts to enable the

ip_forward parameter. Some other applications may disable ip_forward, so the best option is to

add the following to /etc/sysctl.conf.

net.ipv4.ip_forward = 1

Guest configuration

Once the host configuration is complete, a guest can be connected to the virtual network based on

its name. To connect a guest to the 'default' virtual network, the following could be used in the XML

configuration file (such as /etc/libvirtd/qemu/myguest.xml) for the guest:

</interface>

Note

Defining a MAC address is optional. A MAC address is automatically generated if omitted.

Manually setting the MAC address may be useful to maintain consistency or easy reference

throughout your environment, or to avoid the very small chance of a conflict.

</interface>

10.2. Bridged networking with libvirt

Bridged networking (also known as physical device sharing) is used for dedicating a physical device

to a virtual machine. Bridging is often used for more advanced setups and on servers with multiple

network interfaces.

Disable NetworkManager

NetworkManager does not support bridging. NetworkManager must be disabled to use networking with

the network scripts (located in the /etc/sysconfig/network-scripts/ directory).

# chkconfig NetworkManager off

# chkconfig network on

# service NetworkManager stop

# service network start

Note

Instead of turning off NetworkManager, add "NM_CONTROLLED=no" to the ifcfg-* scripts used

in the examples.